Exam 4 Objectives Flashcards
(121 cards)
1
Q
Fecal-oral:
A
Fecal-oral: route of transmission of a disease, when pathogens in fecal particles passing from one host are introduced into the oral cavity of another host.
2
Q
Parenteral
A
Parenteral: taken into the body or administered in a manner other than through the digestive tract, as by intravenous or intramuscular injection.
3
Q
Blood/Body Fluids:
A
Blood/Body Fluids: liquids originating from inside the bodies of living people. They include fluids that are excreted or secreted from the body as well as body water that normally is not.
4
Q
HBcAg:
A
HBcAg: Hepatitis B core antigen that is a protein surrounding viral DNA in the virus core, not detectable in serum
5
Q
HBeAg
A
HBeAg: Hepatitis Be antigen that is a protein surrounding viral DNA in virus core, appears shortly after HBsAg and indicates high viral replication and a high degree of infectivity.
6
Q
HBsAg:
A
HBsAg: Surface antigen, and the first antigen to appear in serum. It is detectable 2-12 weeks post exposure, and peaks during acute infection. Persistent HBsAg is indicative of a chronic or active infection.
7
Q
anti-HBc
A
IgM anti-HBc antibody and the first to appear. It is an isotype antibody against HBcAg and is used as an indicator of current or recent acute infection
IgG anti-HBc antibody appears later and persists for life. It indicates a past infection and usually immunit
8
Q
anti-HBs:
A
anti-HBs: patient antibody that appears during recovery and persists for years and provides protective immunity to reinfection.
9
Q
Identify the main health concern associated with viral hepatitis (acute, chronic, etc.).
A
Acute: hepatitis, highly infective or asymptomatic, hepatosplenomegaly, tenderness, jaundice, fever, fatigue, GI upset (loss of appetite), muscle pain.
Chronic: Cirrhosis and/or liver cancer, chronic infection
10
Q
Recognize the significance of IgM isotype antibody, IgG isotype antibody, and viral Ag or nucleic acid (RNA or DNA) in general staging of viral infections by laboratory testing
A
IgM: indicates a current or recent acute infection due to the fact that IgM falls off as isotype switching occurs and IgG concentrations increase. IgM in newborns will indicate a congenital infection.
IgG: indicates a current or past infection and immunity in most cases. IgG in newborns does not indicate a congenital infection because the antibody can be from passive immunity from the mother indicating that that the baby was infected in utero. If both IgG and IgM are positive, it may indicate a chronic infection.
Viral DNA or RNA: (through molecular diagnostics) indicates a current infection.
11
Q
Hepatitis A Virus (HAV)
Mode of Transmission:
A
Mode of Transmission: Fecal-oral route (foodborne), most common cause of viral hepatitis.
12
Q
HAV incubation period:
A
28 days until patient develops symptoms.
Most infected adults are symptomatic.
Infected children are usually asymptomatic
13
Q
HAV acute or chronic?
A
Acute
Resolves in 1-8 weeks
Rarely fulminant
Virus does not become chronic except in immunocompromised individuals.
14
Q
HAV antibodies used for diagnoses?
A
Ig/Ag useful for diagnosis by serology:
IgM anti-HAV in patient serum indicates acute infection
Total anti-HAV indicates immunity and past infection
HAV vaccination available and recommended for travel to endemic areas and is now part of the childhood vaccination program in the United States.
Intramuscular injections of anti-HAV Ig prevents disease in exposed individuals through passive immunity
15
Q
HEV mode of transmission
A
Mode of Transmission: Fecal-oral route, contracted from drinking water contaminated with feces, primarily in developing countries.
16
Q
HEV acute or chronic?
A
Acute; self-limiting disease
17
Q
HEV consequences of chronicity?
A
Consequences of chronicity: Major concern is associated with a high rate of mortality in pregnant women who become infected, especially if they are infected during their 3rd trimester. Pregnant women are considered immunocompromised
18
Q
HEV antibodies used for diagnosis?
A
Ig/Ag useful for diagnosis by serology: Serological test for IgM anti-HEV has been developed but is not commercially available in the U.S. due to the rarity of infection here.
19
Q
HBV mode of transmission
A
Mode of Transmission: Blood or body fluids (parenteral)
20
Q
HBV incubation period
A
Incubation Period: Long incubation period of 60-90 days prior to disease onset
21
Q
HBV acute or chronic?
A
Acute or Chronic: Both. Highly variable and depends on the age when infected
Acute:
30-50% of adults, so the majority are asymptomatic
22
Q
HBV age group that develops chronic infection?
A
All
23
Q
HBV consequences of chronicity?
A
Consequences of chronicity: Severe liver disease, necrosis, fatality, carrier, chronic infection
24
Q
HBV antibody used for diagnosis?
A
HBcAg: Hepatitis B core antigen that is a protein surrounding viral DNA in the virus core, not detectable in serum
HBeAg: Hepatitis Be antigen that is a protein surrounding viral DNA in virus core, appears shortly after HBsAg and indicates high viral replication and a high degree of infectivity.
HBsAg: Hepatitis B surface antigen, a protein in the outer virus envelope and in blood particles that allows the virus to dock. It is the first antigen to appear in serum.
It is detectable 2-12 weeks post exposure, and peaks during acute infection.
Persistent HBsAg is indicative of a chronic or active infection. Levels decline as patient Ab increases (detectable 12-20 weeks after symptoms)
HbeAg: appears shortly after HBsAg and indicates high viral replication and high degree of infectivity.
IgM anti-HBc: appears first (IgM isotype antibody against the HBcAg) and used as an indicator of current or recent acute infection
Useful for detecting the core window (time between disappearance of HbsAg and anti-Hbs)
When Ig and Ag are present in equal amounts, Ag is not detected by EIA because it is bound up = core window. You can detect the Ig to the core even though you can’t detect the surface antigen any longer
IgG anti-HBc: appears later and persists for life. Indicates a past infection and usually immunity.
Anti-HBs: appears during recovery and persists for years and provides protective immunity to reinfection
Failure to develop anti-HBs indicates chronic infection and the inability to clear surface antigen. This antibody is produced in response to vaccination.
25
HDV mode of transmission
Mode of Transmission: Incomplete virus that only occurs with HBV either simultaneously or as a superinfection of HBV
Uses HBsAg protein in its outer envelope with HBV, because it cannot form infectious protein particles without HBV.
26
HDV acute or chronic?
Acute or Chronic: Results in a greater risk of fulminant or chronic liver disease
27
HDV age group that develops chronic infection?
All
28
HDV consequences of chronicity?
Chronic liver disease
29
HDV antibody used for diagnosis?
Serological testing available for:
IgM anti-HDV: appears 6 to 7 weeks after exposure
IgG anti-HDV: appears during convalescence, then declines after resolution of infection
Both IgM anti-H
30
HCV mode of transmission
Mode of Transmission: Transmitted by contaminated blood but not usually by sexual contact (IV drug use, blood or organ transplants, perinatal transmission)
31
HCV incubation period
Incubation Period: 7-8 weeks
| High mutation rate allows it to escape immune response preventing development of effective vaccine
32
HCV acute or chronic?
Acute or Chronic: 20% develop acute symptoms. 85% develop chronic infection
33
HCV age group that develops chronic infection?
All
34
HCV consequences of chronicity?
Consequences of chronicity: Liver cirrhosis develops in 20% of those with chronic infection 20-25 years later. This increases the risk of Hepatocellular carcinoma (liver cancer).
35
Antibody used for diagnosis of HCV?
Anti-HCV by EIA
7-8 weeks post exposure
99% specificity, 1% false positives - must do confirmatory test
Confirmatory test = RIBA (Recombinant Immunoblot Assay)
Molecular assay for HCV RNA
HCV Molecular Testing
Earlier detection than EIA (1 week post exposure)
Detects infection in babies
Detects exposure in immunocompromised individuals
Used for viral load testing to follow response to drug therapy
HCV Genotyping
1a & 1b more common in U.S. than 2 & 3
Genotyping combined with HCV RNA to predict response to pegylated-interferon-α and Ribavirin treatments
Aka polyethylene glycol and IFN-α, coupled together to increase its half-life in serum
Low HCV RNA = Good prognosis
2 & 3 respond after 24 weeks of treatment
1 is a poor response and requires 48 weeks of therapy
1a and 1b more common than 2 and 3
36
Explain how a RIBA test (such as that used to confirm HCV infection) differs from a western blot test.
Recombinant Immunoblot Assay
The RIBA test is a confirmatory test similar to the Western blot, except that recombinant HCV proteins are blotted directly onto nitrocellulose membranes.
RIBA is a confirmatory test for for the presence of antibodies to HCV, whereas Western Blot is a confirmatory test for HIV.
A positive RIBA confirms that you had been exposed to the virus, while a negative RIBA indicates that your first test was probably a false positive and you have never been infected by HCV
A positive (or detectable) HCV RNA means that you are currently infected by HCV.
37
Given the results of “hepatitis panel” tests for acute viral hepatitis, interpret the disease that the patient has and suggest whether further testing is warranted and what that testing should be.
Panel results help to determine if the cause of Hepatitis is viral associated. If so, which virus.
IgM anti-HAV: used for Hepatitis A Virus
If positive, no further testing warranted.
Monitor patient, send home with therapy.
IgM anti-HBc and HBsAg: used for Hepatitis B Virus
HbsAg detects acute Hepatitis B infection
Monitor patient, follow up aggressively
anti-HCV and HCV RNA: used for Hepatitis C Virus
HCV RNA: qualitative test, becomes positive earlier than the anti-HCV test.
+ anti-HCV requires confirmatory testing
If both anti-HCV and HCV RNA are included in the panel, HCV RNA will serve as the confirmatory test.
Stage disease, determine whether patient will resolve the acute infection or advance to chronic infection
38
TORCH testing:
TORCH testing: (Toxoplasmosis Other infections, Rubella, Cytomegalovirus and Herpes Simplex virus) often performed in young women of childbearing age because of consequences of acute infection in utero or for newborns if acute infection is transmitted from mother to baby
39
Heterophiles antibody:
Heterophile antibody: IgM antibodies that are capable of reacting with similar antigens from two or more unrelated species. They are found in other cases besides IM and are detected with extract of bovine rbc antigens.
40
Herd immunity:
Herd immunity: protection from spread of infection by vaccination-induced population immunity
41
Identify which viruses (other common names) belong to the Herpes Virus Family.
Epstein-Barr Virus (EBV or Human Herpes Virus-4 (HHV-4)), Cytomegalovirus (HHV-5), Herpes Simplex Virus (HSV-1 and HSV-2), Varicella-Zoster Virus (HHV-3), Other human herpes viruses (HHV-6, HHV-7, HHV-8).
42
Identify the disease caused by Epstein-Barr Virus (EBV), the immune cell target of EBV and the receptor that it uses to target that cell, and the effect of EBV on the infected cell.
Cause of Infectious Mononucleosis (Mono) in young adults. EVB infects epithelial cells of the oropharynx and B lymphocytes via CD21. Infected B cells undergo polyclonal activation, proliferate and secrete antibody
43
Associate detection/screening for heterophile antibodies with diagnosis of infectious mononucleosis.
Heterophile antibodies used for diagnosis
Heterophile antibodies are IgM antibodies that are capable of reacting with similar antigens from two or more unrelated species (for EBV, sheep and cows are the unrelated species)
Heterophile Ab are found in other cases besides IM, but the term “heterophile antibody” is now reserved to designate IM
For IM screening with Monospot test, heterophile antibodies are detected with extract of bovine (cow) rbc antigens
44
Identify confirmatory testing for EBV infection, and the significance of these tests in disease staging
Because ~20% of people with EBV do not make heterophile Ab (which results in a false negative), must do other tests:
IgM anti-VCA (viral capsid antigen) indicates acute disease
IgG anti-VCA (viral capsid antigen) indicates previous infection / convalescence
Anti-EBNA (EBV nuclear antigen) persists for life (immunity)
45
Identify the patient populations at greatest risk from cytomegalovirus (CMV) infection and the possible consequences of infection.
Around 90% of adults have been infected by CMV
Usually asymptomatic in healthy individuals but can be very severe in immunocompromised and newborns.
Most common cause of congenital infections throughout world (0.3-2% of all live births).
10% of infected babies exhibit symptoms of CNS and/or multiple organ infection
5% of these infants will die
50% of surviving symptomatic babies have long-term consequences such as hearing loss, mental retardation and vision loss
46
Identify the problems associated with serological testing for antibody to CMV and the preferred methods of detecting CMV infection in the at-risk populations.
Assays for IgM anti-CMV have false negatives in newborns and immunocompromised, and false positives from rheumatoid factor
Rapid detection not readily available
Newest EIA assay for acute disease diagnosis measures “low avidity IgG” antibody (prior to affinity maturation) which is not widely available in U.S yet
Most reliable diagnostic tests for acute CMV infection are performed on saliva, urine or throat swab samples and include:
Shell vial: cultures for viable virus can detect infection in 24-72 hours
Qualitative PCR: DNA also gives rapid results and can help to stage disease and monitor effectiveness of antiviral therapy
47
Identify the target tissue of HSV-1 and HSV-2 viruses and which is of most concern.
HSV-2 is more serious
HSV-1:
Virus hides in dorsal root ganglia and reactivates as “cold sores” or “fever blisters”
Can be a cause for concern in children who may develop ulcerating lesions of the guns (gingivostomatitis) and/or conjunctivitis
HSV-2:
Sexually-transmitted disease (STD) affected ~17% of population between ages 14-49
Causes genital lesions with fever, inguinal lymphadenopathy and dysuria
Reactivates from nerve cells many times throughout life in normal individuals (no cure)
Infants can have localized infections of skin, eyes, or mucosa transmitted from infected mother, or may get disseminated infection leading to death
Immunocompromised patients can get very severe localized infections or disseminated disease such as herpes encephalitis
48
Identify the testing available for detection of HSV-1 and HSV-2 infection, whether the Ag or Ab to the virus is detected by serology, and which test is currently able to distinguish between HSV-1 and HSV-2
Serological testing by EIA, latex agglutination for viral Ag, or culture in shell vial followed by immunofluorescent staining are available for HSV-1 and HSV-2, but lack sensitivity
PCR detects viral DNA and can distinguish between HSV-1 and HSV-2 (rapidly replacing culture as the preferred method of detection but can only be used when active lesions are present to obtain sample)
49
Identify the two diseases caused by Varicella-Zoster Virus (VZV) and the reason why the viral infection reactivates.
```
Varicella (aka Chicken pox) as an acute disease
Herpes zoster (aka Shingles) as a reactivation of latent disease
```
50
Identify the methods used to detect VZV infection versus immunity to VZV.
Shell vial culture method coupled with immunofluorescent staining to identify the virus
PCR for VZV DNA detection is rapidly become the laboratory test of choice
Serology (EIA) used for establishing immunity to VZV; >90% of population is immune either from natural infection or vaccination by live attenuated varicella vaccine; 4-fold rise in paired acute/convalescent titers is diagnostic
51
Identify the disease caused by Rubella virus and the most serious infection caused by Rubella.
German measles - normal
| Most severe: Congenital Rubella Syndrome
52
Identify the methods used to detect Rubella infection and how a significant titer is interpreted in regards to post-vaccination or as an indication of current infection.
Post-vaccination anti-Rubella IgG antibody level of >15 IU/mL indicates immunity in a prospective mother; EIA with synthetic Rubella peptides as the target test antigen is most common serological test
Pregnant mother with suspected acute infection: a 4-fold rise in IgM titer in samples drawn 5 days apart indicates current acute infection (e.g. 1:4 titer on first sample, 1:16 on second sample would be indicative of mother with acute infection when samples are tested at the same time by the same laboratory)
IgM anti-Rubella in newborn indicates congenital disease (confirmed by positive culture of PCR for Rubella RNA)
No IgM or IgG means the person has not been vaccinated or infected
53
Identify the causative agent of syphilis, the 2 primary modes of transmission, and the usual treatment of the disease if diagnosed early.
Causative agent of syphilis: Treponema pallidum (spirochete)
Primarily a sexually-transmitted disease (STD), but may cause congenital infection as well
Disease is easily treated with penicillin, especially in early stages
54
Nontreponemal tests:
use a test antigen consisting of a solution of cholesterol, lecithin, and cardiolipin to detect reagin antibodies
55
Reagin:
Reagin: antibodies to cardiolipin that are not specific to syphilis, but actually due to antigen released by cell damage
56
Treponemal tests:
Treponemal tests: detect antibody specifically to treponemal antigens
57
Flocculation:
Flocculation: microscopic precipitation
58
List the 4 stages of syphilis, the symptoms of each stage, and the time-frame in which each stage may be observed (following initial infection).
Primary syphilis:
well -defined painless lesion with an ulcerated center and red raised border forms
Usually on genitals
Lesion will resolve on its own if untreated
Secondary syphilis:
Occurs in 25% of untreated infections
Organism spreads through body and causes generalized lymphadenopathy and flu like symptoms
Lesions common on trunk, palms of hands and soles of feet are highly contagious
Latent syphilis:
No symptoms for one to many years despite organism presence
Tertiary syphilis:
Develops 10-30 years later in about 30% of those who have latent syphilis
59
List the three general types of testing available for diagnosing syphilis, the usual use of each general type of test, and categorize each specific test discussed in lecture into each of these general types.
Direct spirochete detection in lesion fluid (based on corkscrew shape and flexing motility; not specific for syphilis because of normal flora)
Nontreponemal tests: use a test antigen consisting of a solution of cholesterol, lecithin, and cardiolipin to detect reagin antibodies
Classic screening tests
Venereal Disease Research Laboratory (VDLR)
Rapid Plasma Reagin Test (RPR)
Treponemal tests: detect antibody specifically to treponemal antigens
EIA and CIA
Fluorescent Treponemal Antibody Absorption Test
T. pallidum Particle Agglutination
60
List the components of the test antigen (reagent) used for nontreponemal tests for syphilis.
VDRL
Suspension of cholesterol + lectin + cardiolipin mixed with patient serum
RPR
Same basic reagent as VDRL except added charcoal
61
Identify the only test that is currently approved to diagnose tertiary neurosyphilis and the patient sample used for this testing.
Nontreponemal test-VDRL
62
Identify which type of test for syphilis loses sensitivity during the tertiary phase of infection (i.e. can give a false negative result in a patient who really has tertiary syphilis).
VDLR/RPR: treated patients typically have negative results 1 year following successful treatment
63
List the proper order of screening and confirmatory testing for syphilis, as it was classically performed, and how this has changed now with newer “reversed order” syphilis serology testing.
The traditional order was with nontrep. as screening test and trep as confirmatory test. Now, Trep. EIA or CIA in 96 well plates is used for screening, and Nontrep RPR is used to confirm. Reversed it because of 2% false negatives. Trep EIA will always be positive if you’ve had the disease before. You can re-catch syphilis.
64
Identify the causative agent of Lyme disease, the characteristic symptom of primary infection that is observed in 80% of patients, and disease sequelae that may be seen in chronic infection.
Causative agent: tick-borne infection caused by Borrelia burgdorferi
Erythema migrans rash= bulls-eye rash seen by 80% of patients about 1 week following tick bite
Symptoms seen in chronic infection: large joint arthritis (most common)
65
Identify the screening test for Lyme disease, whether a positive is diagnostic, and whether a confirmatory test is necessary (if so, ID the confirmatory test).
EIA/FIA
| Patient samples with equivocal or positive screening test are retested using western blot (confirmatory test)
66
Identify possible causes of biological false positive results in Lyme disease serology testing.
```
False positives occur with:
Syphilis and other treponemal diseases
Infectious mononucleosis
Autoimmune diseases
Rocky mountain spotted fever
```
67
List the main distinguishing features of Group A b-hemolytic streptococcus (S. pyogenes) used to identify the organism in a microbiology laboratory.
B-hemolytic
Gram-positive cocci in chains
Lancet Group A (M protein)
68
M protein:
M protein: helps the organism evade innate immune cell defenses
Prevents phagocytosis
Inhibits C3b deposition on bacterial surface
69
Streptococcal pyrogenic exotoxin A1 (SpeA1):
Streptococcal pyrogenic exotoxin A1 (SpeA1): second virulence factor that acts as a superantigen
70
Describe how a superantigen activates T lymphocytes
Superantigens cause non-antigen specific activation of large numbers of T lymphocytes by holding MHC and TCR together
71
4) Describe the main clinical features of Impetigo and Group A Streptococcal pharyngitis. Identify which (or both?) is associated with Scarlet Fever, Rheumatic Fever, Acute Proliferative Glomerulonephritis, and Toxic Shock Syndrome.
Strep Pharyngitis: Causes strep throat (Associated with Scarlet fever and Rheumatic fever)
Streptococcal pyoderma: Causes skin infections. If the infection is present on the face, it is known as “impetigo” (Associated with either Strep throat or Strep pyoderma, but most commonly the latter)
72
What is the main drawback of rapid testing for Strep Throat?
Rapid testing for strep throat is only 80% sensitive so it provides many false negatives
Negative rapid strep testing should be followed by culture in cases of suspected strp pharyngitis
73
Compare and contrast the efficacy of the ASO, anti-DNase B, and Streptozyme assays in diagnosis of past Group A Strep infections (Impetigo and Strep Throat).
ASO test
Historic red blood cell lysis assay test: rarely performed in clinical labs any longer
Newer version of assay is performed by nephelometry to detect streptolysin O
ASO test is positive in 80% of strep throat cases, but does not become positive in strep pyoderma (lacks sensitivity)
Anti-Dnase B assay is more sensitive than ASO and will be positive in cases of streptococcal pyoderma
Can be performed by colorimetric assay
Nephelometry most cost effective
Streptozyme test is a slide red blood cell agglutination screening test
Significant false positives and negatives (in children)
Recommended that at least two separate test formats be performed to achieve 95% sensitivity for Group A Strep sequelae detection
74
RAST:
Radioallergosorbent Test
75
RIST:
RIST: (Radioimmunosorbent Test) Total serum IgE measured by chemiluminescence as a screening tool.
Disadvantages:
not sensitive (⅓ people with allergies have normal total IgE)
Does not identify the offending allergen
Advantages:
Inexpensive
Suggests further testing
76
Explain the immune system mechanism responsible for each of the 4 types of hypersensitivity reactions, including the isotype of the antibody involved (as appropriate) and/or effector cell types acting in each.
1: IgE mediated, mast cell degranulation, asthma/ hay fever
2: IgG Antibody-mediated cell surface reactions that cause cytotoxicity, complement activation. Hemolytic anemia, HDFN
3: IgG Immune complex mediated (soluble), complement activation. Local inflammation, Arthus reaction 4: no Ab, cell mediated, sensitized T cell, activated macrophages. Contact dermatitis
77
Explain how an “immediate hypersensitivity” differs from a “delayed-type hypersensitivity (DTH)” response, and what type of hypersensitivity (I – IV) is being tested for by each.
Immediate: 15-30 min, Type I. an antigen is presented to CD4+ Th2 cells specific to the antigen that stimulate B-cell production of IgE antibodies also specific to the antigen
DTH; Type IV. 1-3 days, Not antibody mediated but cell-mediated
78
Identify which hypersensitivity is associated with histamine release.
Type I Hypersensitivity
79
Identify the major granulocyte that plays a role in allergic and parasitic diseases, the antibody isotype that triggers its degranulation, and the unique components of this cells granules.
Mast cells. IgE bound to Fc(epsilon)RI (IgE Fc receptors of Mast cells) leads to degranulation and activation. 10% of total mast cell granule content is Histamine, prostaglandins and leukotrines are present too
80
Describe the utility of total serum IgE testing, skin prick testing, and allergen-specific laboratory testing, listing the advantages and disadvantages of each.
IgE: measures blood levels of IgE. Initial screen for allergies. Pros: cheap suggests further testing. Con: lack of specificity, doesn’t identify antigen and can miss things. (RIST) Skin: looks for 3mm swelling after 15-30 minutes. Cons: danger of systemic reaction, is traumatic, and tests for limited allergens. Pros: positive test is clinically significant
Allergen Specific: (RAST) can test for total IgE and also huge array of allergens. Cons: less specific than skin, only tells if IgE is present, physician may miss culprit allergen. Pro: can be used if on anti-histamine, only requires one skin puncture
81
Identify common causes of type II hypersensitivities.
Blood transfusions. Erythroblastosis fetalis. Hemolytic anemia.
82
What type of hypersensitivity is responsible for serum sickness?
Type III
83
What type of hypersensitivity is responsible for celiac disease?
Type IV
84
What type of hypersensitivity is responsible for poison ivy
Type IV
85
What type of hypersensitivity is responsible for allergic asthma
Type I
86
What type of hypersensitivity is responsible for food allergy
Type I
87
Identify which hypersensitivity responses involve complement activation.
Type II and III
88
Identify which hypersensitivity responses involve complement activation.
Type II hypersensitivity: auto-antibodies againts cell surface or extracellular matrix proteins (most common)
Type III hypersensitivity: formation of soluble immune complexes that deposit in tissues (joints or kidney glomeruli) leads to systemic autoimmunity
Type IV hypersensitivity: effector t cells directly destroy body cells
89
Identify four autoimmune diseases that have a much higher incidence rate (> 5 times) in women than in men.
Hashimoto’s thyroiditis
Graves’ disease
Systemic lupus erythematosis
Addison’s disease
90
Describe the general cause of Celiac Disease, auto-antibodies that can be sed to diagnose it, and why dermatitis herpetiformis is associated with this disease.
Gluten sensitivity necessitating a gluten-free diet (no wheat, barley, rye)
Cause: during digestion, tissue transglutaminase (TTG) deamidates the gliadin component of gluten, and the modified gliadin stimulates a T cell response
Auto-Antibodies used for diagnosis:
IgA Anti-TTG (Tissue Transglutaminase)
IgA Anti-Gliadin
IgA Anti-endomysium (Smooth muscle connective tissue)
Dermatitis Herpetiformis
If continue to eat gluten (even though have gluten allergy) you will get this.
Its associated with high Serum IgA Anti-TTG
91
Identify the two forms of Inflammatory Bowel Disease in humans, which can be associated with ANCA, and which ANCA pattern it is associated with (cANCA or pANCA).
Ulcerative colitis - inflames the large intestine only and spares the anus
pANCA (peripheral anti-neutrophil antibodies)
● Wegener’s granulomatosis- autoimmune vasculitis
cANCA (cytoplasmic anti-neutrophil antibodies)
● Other IBD: Crohn’s disease - can affect any part of the intestinal tract (mouth to anus) an is associated w/ “skip lesions” (healthy and diseased tissue alternates)
92
Identify the autoantibodies associated with Pernicious Anemia and the vitamin deficiency they can cause.
Megaloblastic anemia due to cobalamin (vitamin B12) deficiency
Antibodies interfere with uptake of cobalamin from intestine
● Associated with 2 antibodies for diagnosis
Anti-Intrinsic Factor AntiBody
most common (70% of patients)
B. Anti-Parietal Cell Antibody
● Vitamin B12 deficiency
Require monthly injections of cobalamin
93
Identify the auto-antigen that is targeted in Myasthenia gravis, the disease pathophysiology, the immune mechanism(s) responsible for the disease, and the laboratory test used for diagnosis.
● Neuromuscular disorder with fatigue and skeletal muscle weakness
○ Due to Ab to acetylcholine receptor
■ Acetylcholine (ACH) is released from motor neuron ending and binds to ACH-R on muscle fiber to initiate action potential
■ Ab blocks binding to ACH-R and also increases receptor uptake by the muscle cell (decreasing available receptor)
○ Lab diagnosis by detection of anti-ACH-R Ab by precipitation radioimmunoassay (RIA)
94
Identify the auto-antigens that are targeted in Multiple sclerosis, the disease pathophysiology, and the immune mechanism(s) responsible for the disease.
● MS is an inflammatory autoimmune disease of the myelin located in the CNS
○ Autoantigens include:
■ MBP=myelin basic protein
■ MOG= myelin oligodendrocyte glycoprotein
○ These autoantigens are targeted by both Ab and T cells (Th1 and Tc)
○ Both Tc and antibody play a role in myelin destruction
● Symptoms:
○ Destruction of myelin sheath around axons causes visual problems, weakness, uncontrolled limb movement, loss of balance, and pins/needles sensations
○ MS presents in two ways in affected patients:
■ Chronic progressive disease..
■ Acute relapsing/remitting
○ No reliable lab test for diagnosis
■ (MRI for lesions in brain or spinal cord used)
95
Identify the two most common rheumatologic diseases that are considered autoimmune diseases.
Systemic lupus erythematosus
| Rheumatoid arthritis
96
Explain why autoimmune rheumatologic diseases are difficult to diagnose.
Symptoms overlap from one disease to another
| Laboratory test results overlap (no test is completely specific or sensitive for a given disease)
97
FANA -
FANA - fluorescent antinuclear antibody
Results include both titer and pattern of antibody binding
Homogenous - even staining of entire nucleus
Speckled - nucleus stains evenly except for centromeres
Nucleolar - large discrete staining of nucleoli only
Peripheral - nuclear rim staining
Mixed - a mixture of the above patterns
98
ANA
ANA - antinuclear antibodies
99
ENA -
ENA - extractable nuclear antibody
| Anti-dsDNA and Anti-sm are diagnostic for SLE but are not very sensitive
100
Categorize the autoimmune mechanism responsible for Lupus as one of the Type I-IV hypersensitivity responses
Type III hypersensitivity
101
Describe how titer is important in interpretation of FANA and what the maximum titer is that is still considered normal.
Titer is important because it helps to determine how much antibody is present. It is a serial dilution of the concentration of antibodies in a person until reactivity is no longer present.
Less than or equal to 1:80 is Negative
Greater than or equal to 1:160 is Positive
102
Identify other diseases that may show a low positive titer in an FANA test, as well as other “non-disease” states.
Low positive titers are present in RA, Scleroderma, Sjogren’s, etc.
Positive FANA does not diagnose SLE
Positive FANA is usually reflexed to follow-up ENA tests for specific antibodies to extractable nuclear antigens performed by EIA
103
Identify the specific ENA that is associated with drug-induced lupus.
Anti-histone
104
Explain why lupus patients can have a false positive syphilis test. Choose whether this false positive would be in either the non-treponemal or treponemal test for syphilis, or both.
Non-treponemal because with lupus you can produce anticardiolipin. Non-treponemal tests for cardiolipin, in lupus you have antibodies for cardiolipin
105
Define “rheumatoid factor” (RF) and identify what diseases it may be found in, and for which disease it is considered most significant.
RF is IgM, IgG, or IgA antibody to the Fc portion of IgG (anti-immunoglobulin antibodies)
significant for RA, but also can be in SLE, Sjogren's and MCTD (mixed connective tissue disease)
106
Describe how the screening test for IgM isotype RF differs from the specific tests for IgG and IgA isotypes of RF. Which is/are most specific for diagnosis of RA?
RF is not specific because only IgM will cause agglutination. Specific IgG and IgA testing by EIA or nephelometry are much more disease-specific
107
Define the antigen used for anti-CCP testing, the disease this antibody is associated with, and its usefulness in relation to RF testing.
The antigen is citrulline. It is associated with rheumatoid arthritis when done in parallel with RF test, has 98% specificity
108
Identify the diagnostic criteria used for RA and whether it is necessary for the RF and/or anti-CCP tests to be positive or not.
Expanded diagnostic scoring system, must score at least 6 out of 10 points to diagnose RA. Depends on number of joints involved, serology (RF and anti-CCP), Acute-phase reactant testing (CRP and ESR), duration of symptoms. Due to the point system, you could be diagnosed without testing positive for either test.
109
Recognize the laboratory tests that may be used to follow the course of SLE and RA, and whether the results will be abnormally high or abnormally low in uncontrolled disease flares.
Following SLE: INCREASE: C-reactive protein (CRP), erythrocyte sedimentation rate, anti-dsDNA titer, urine protein (glomerulonephritis).
DECREASE: CBC (WBC, RBC, platelet), Complement (C3, C4, CH50), and serum albumin.
Progress of RA: INCREASE: Erythrocyte sedimentation rate (increased), C-reactive protein (increased),
DECREASE: complement components (C3 and C4 usually decreased during acute attacks
110
Identify whether CD4+ T cells, CD8+ T cells, and/or B cells are responsible for autoimmune disease.
Autoimmune disease is due to a failure in lymphocyte tolerance, either from CD4, CD8, or B Cells. (breach of at least 2 populations)
111
Identify two proteins involved in self tolerance that when defective in humans lead to generalized autoimmune disease.
AIRE
| FoxP3
112
Explain how an allele of CTLA-4 normally found in the human population can lead to increased susceptibility to autoimmune disease.
One allele of CTLA4 limits production of soluble CTLA-4 which could be important in Treg function
○ Weak risk factor
○ Allele is present in 50% of population, increases to 60% in patients with autoimmune diseases
○ not associated with increased risk for a particular autoimmune disease, but instead autoimmunity in general
○ Suppression of autoreactive T cells by regulatory t cells requires then to interact with the same APC
113
Define “relative risk” and the ultimate effect that it has on an individual’s likelihood to develop any given autoimmune disease. Be able to use disease incidence and relative risk to calculate actual risk for an individual who may have an “at risk” allele.
Relative Risk is the assumption that if you have the associated HLA allele, RR is the increased risk you have over the general population to get the disease.
Ex. If total Risk in population is 1 in 100,000 and RR is 3.5, Your actual risk ir 3.5 in 100,000 or 1 in 26,600
114
Explain the role of HLA alleles in development of autoimmunity (i.e. what are the HLA molecules doing exactly to trigger autoimmunity?).
Human HLA (MHC class 1 and 2) are linked to increased or decreased susceptibility to certain diseases
Fails to provide specific protection
HLA helps in antigen processing when MHC presents self-antigen
People with certain HLA Ag are more likely to develop certain autoimmune diseases
115
List and explain the mechanisms of at least six (6) factors that have been proposed to be risk factors for autoimmune disease development besides gender and HLA alleles. In doing so, be sure to define the term “hapten”.
Environmental
Release of sequestered antigens
Inflammation causing ectopic expression of MHC class II
Molecular mimicry
Polyclonal B cell activation
Plant mitogens cause polyclonal lymphocyte activation
Minor defects in the immune system itself
Chemical “Environmental”
Act as a hapten to change “self-proteins” into noel antigens
Paraneoplastic - caused by immune response to a cancer in a patient
Epitope spreading
116
Define epitope spreading (in the context of autoimmune disease) and how linked recognition is responsible for epitope spreading.
● When a patient is first diagnosed (or prior) auto Ab are limited
● As the autoimmune disease progresses, the patient develops auto-Ab against more and more auto-Ag
● This is thought to be due to the “sloppiness” of T cell help to B cells
● Epitope spreading in SLE
○ Cd4 t cells specific for one epitope of a macromolecular complex can provide help to B cells specific for other accessible epitopes of the complex
○ A B cell that internalizes a macromolecular complex can present Ag to T cells specific for any of the proteins in the complex. To get t cell help and present Ag
○ Bcr and tcr have linked recognition and it can recognize them
117
Discuss the general usefulness of IVIg, RhoGAM, and other antibody preparations used in the therapeutic treatment of humans.
Used in human medicine
IVig: concentrated human IgG pooled from multiple “normal” donors
Used as interfering auto-idiotype ab to block autoantibodies
RhoGAM: used in prevention of hemolytic disease of the newborn
Polyclonal Ab purified from pooled Rh-negative Mom’s who have anti Rh antibody
Monoclonal antibody: or recombinant protein “therapies” used to target and kill tumors or as immunosuppressants
Oncology
118
Describe the general process of hybridoma creation for the production of monoclonal antibodies.
Fusion of two original cells (plasma cell and an immortalized myeloma cell line)
1. Inject (immunize) animal (mouse) with an antigen so the animal will make antibody to the antigen
2. Isolate B cells (plasma cells) from the spleen of the animal, and fuse the B cells to an immortalized myeloma
3. Grow “fused” cells in chemical selection media so that only cells that have fused B cell and myeloma can survive (unfused spleen cells and myeloma cells will die)
4. Single-cell clone the surviving “hydridoma” cells and select for a clone that produced high affinity antibody against the antigen you used to immunize the animal (your target antigen)
5. Isolate the pure monoclonal antibody from this hybridoma cell line
119
Describe how monoclonal antibody preparations differ from polyclonal antibody preparations (aka, antiserum).
● Reagents for test kits clinical laboratory testing and research
Immunohistochemistry, clinical chemistry nephelometry testing, EIA, flow cytometry, virtually any test that relies on antigen identification using an antibody
● Treatments for infusion into humans (exploding market)
● Poly Clonal
Mixture of different isotypes and different affinities
Good for treatment
Basically serum
● Monoclonal- come from one B cell
One single isotype with one single affinity
Good for diagnosis
**Can bind to all
Antibody is all identical in monoclonal
120
Identify specific monoclonal antibody therapies used to treat Rheumatoid Arthritis and other destructive autoimmune disorders.
● Treatment of specific cancers
● Immunosuppressive uses of mAb
Anti-TNFalpha: blocking mAb used to treat rheumatoid arthritis (blocks joint destruction)
Anti-alpha4 integrin-blocks “homing” of inflammatory cells preventing autoimmune tissue destruction (MS, IBD, psoriasis)
Anti-IL-1 or anti-IL-6 antibodies to interfere with macrophage inflammatory cytokines when anti-TNF-alpha does not work
121
What are HAMA? Would they cause false positive of false negative assay results in clinical laboratory EIA testing?
HAMA = human anti-mouse antibodies
Generally cause a false positive result that does not correlate with patient history
Cause false positive if antibodies against another species are present
