Flashcards in Day 2.3 Immuno Deck (122):
What HPS types are Ab-mediated?
(Type IV is Tcell mediated)
How are Type II and Type III different in terms of Ab?
Type II has Ab against self. This induces macrophages to eat the self and causes tsu dmg.
Type III has Ab against non-self, and it's the Ab-Ag complex that gets deposited into tissues. This induces macrophages to eat the complexes and cause dmg.
In both cases, the dmg is due to macrophages.
Note: Some disorders which feature Type III and Type IV HPS have anti-self Ab. Just bc there is anti-self Ab doesn't mean the rxn will be Type II.
But, all Type II rxns are mediated by anti-self Ab.
How long does it take for...
Type I HPS?
Type I = 15 min
Type III = 5-12 hrs
Type IV = 24-48 hrs (delayed)
Type I HPS
Anaphylactic and atopic.
Free Ag cross-links IgE on presensitized mast cells and basophils- these degranulate and rls vasoactive amines that act at post-capillary venules (histamine).
How do you test for Type I HPS?
Scratch test (scratch back and put Ag there, wait for 15 min to see well-defined wheal and flare.
What is wheal and flare?
Wheal = hive
Flare = red
Examples of Type I HPS
Anaphylaxis: bee sting, food/drug allergy
Allergic/Atopic: rhinitis, hay fever, eczema*, hives, asthma
Even tho eczema is Tcell mediated, it is a Type I bc it's fast!
Type II HPS
Antibody mediated- IgM, IgG bind to fixed Ag on "enemy cell" (which is actually self!), leading to lysis by complement, or to phagocytosis.
Ab and complement lead to MAC.
Dz is usually specific to the tsu/site where Ag is found
What are the 3 mechanisms of a Type II HPS rxn?
1. Ab opsonize cells or activate complement
2. Ab recruit neutrophils and macrophages that incite tsu dmg
3. Ab bind to normal cellular receptors and interfere w functioning.
What is the test for Type II HPS?
Coombs (direct and indirect)
Use a known marker that binds to Ab to see if the Ab are there.
What is a direct Coombs test?
Anti-Ig antibody is added to the patient's RBC agglutinate to see if RBCs are coated with Ig.
What is an indirect Coombs test?
Normal RBCs are added to the patient's serum agglutinate to see if the serum has anti-RBC surface Ig
Ex of Type II HPS rxn
Auto-immune hemolytic anemia
ITP (Ab against plts)
Erythroblastosis fetalis (Rh incompatibility)
Acute hemolytic txfsn rxns (wrong blood type)
Goodpasture's synd (vasculitis)
Graves' dz (Ab against TSH receptor- stim the receptor --> hyperthyroidism)
Myasthenia Gravis (Ab against Ach receptor)
Type II HPS: What is pernicious anemia?
Have Ab against intrinsic factor (IF) so Vit B12 can't be absorbed in the ilieum.
B12 deficiency (neurologic problems)
Type II HPS: What is erythroblastosis fetalis?
Maternal Ab to a fetal RBC Ag. (Fetus is Rh+ but mom is Rh-, so mom makes Ab against fetus since it's "foreign").
anemia d/t hemolysis of fetal RBC by maternal Ab
jaundice (Hb was broken down, so excess bilirubin --> jaund)
Hydrop fetalis (generalized fetal edema- fluid in lungs, peritoneum, tsus)
Rh- moms don't have Rh-D on the surface of the blood cells. When should they get anti-Rh-D Ig?
28 weeks (bc fetus can be born after this time)
Any traumatic event in which mom might be exposed to fetal RBC (ex: MVA)
W/in 3 days of delivery
Abortion or miscarriage
For which pregnancies will the mom's anti-Rh Ab have an effect?
All pregnancies after the 1st one. (Incl if the first one ended in abortion/miscarriage).
The Ab develop in the 1st pregnancy, but are not in lg enough quantity to cause harm until 2nd pregnancy.
Type II HPS:
What is bullous pemphigoid and pemphigus vulgaris?
Bullous pemphigoid = Ab against hemidesmosomes
Pemphigus vulagaris = Ab against desmosomes / desmoglien
Both of these are Ab against epithelium, so they manifest in skin.
Type III HPS
Ab against non-self Ag, form Ag-Ab immune complexes and get deposited into tsu.
Ag-Ab (IgG) complexes activate complement, which attracts neutrophils.
Neutrophils rls lysosomal enz.
Imagine immune complex as 3 things stuck together: Ag-Ab-complement
What are 2 special kinds of Type III HPS?
What is the mechanism of serum sickness?
Type III immune complex dz in which Ab to foreign proteins are produced (takes 5 days). Immune complexes form and are deposited in membranes, where they fix complement and cause dmg to the tsu.
In past before Abx, gave lots of Ab to the dz, so it would mk complexes and deposit in vessel walls (so, "serum" sickness). Now, it's usually caused by drugs.
Symptoms of serum sickness?
Type III immune complex dz.
Fever, urticaria, arthralgias, proteinuria (and glomerulonephritis), and lymphadenopathy.
Occurs 5-10 days after Ag exposure, bc Ab to the Ag have to be produced.
What is the mechanism of Arthus reaction?
Type III HPS, local, sub-acute, Ab-mediated.
Intradermal injection of Ag (eg tetanus vaccine) induces Ab, which form Ag-Ab complexes in skin.
Test for it w. immunofluroescent staining.
Symptoms of Arthus rxn?
Type III HPS
Edema, necrosis, activation of complement.
5-12 hrs after intradermal injection of Ag.
Ex of Type III HPS
HPS pneumonia (farmer's lung)
Can be assoc'd with vasculitis and systemic manefestations
Type IV HPS
Delayed, T-cell mediated.
Sensitized Tcells encounter Ag and then rls lymphokines which lead to macrophage activation.
No Ab are involved.
Bc it's cell mediated, it is not transferable by serum.
Test: patch test (e.g. PPD for TB)
What are the 4 T's of Type IV HPS?
T-lymphocytes (Tcell mediated)
TB skin tests
Touching (contact dermatitis)
Mnemonic for HPS rxns: ACID
Anaphylactic and Atopic = Type I
Cytotoxic (Ab-mediated) = Type II
Immune complex = Type III
Delayed (Tcell mediated) = Type IV
Ex of Type IV HPS
DM Type I
Graft v Host dz
PPD (test for M. TB)
What are ex of contact dermatitis (Type IV delayed HPS)
Poison ivy, oak
Nickel allergy- watch, belt buckle, sandal buckle
Anti-nuclear Ab (ANA)
but also many other things:
Specific for SLE
dsDNA = even more specific for renal dz in SLE
Anti-IgG (Rhematoid Factor)
This is IgM Ab attacking IgG
Anti-Scl70 (Anti-DNA topoisomerase I)
Primary biliary cirrhosis
Celiac dz (malabs syndrome where villi of gut are severely atrophied)
Gliadin - component of wheat
Goodpasture's synd (renal dz, lung dz)
Anti-U1 RNP (ribonucleoprotein)
MCTD (mixed CT dz)
Anti-glutamate decarboxylase (Anti-glutamic acid decarboxylase)
DM Type I
c-ANCA (Anti-neutrophil cytoplasmic An)
Pauci-immune crescentic glomerulonephritis
Graves' Dz (HYPERthyroidism- the receptor is stimulated)
Illnesses with elevated ESR
Disease activity in RA and SLE
Infection, Inflammation, Malignancy
Osteoarthritis- infection of bone, can be subclinical. if high ESR, increased suspicion; if not, can rule it out.
22q11 deletion syndromes
Due to aberrant devt of 3rd and 4th brachial pouches
Thymic aplasia (--> Tcell deficiency)
Hypocalcemia (secondary to parathyroid aplasia)
DiGeorge = thymic, parathyroid, cardiac defects
Velocardiofacial syndrome = palate, facial, cardiac defects
Which immune deficiencies are B-cell disorders?
Selective Ig deficiency
CVID- common variable immunodeficiency
Which immune deficiencies are T-cell disorders?
Thymic aplasia (DiGeorge)
IL-12 receptor deficiency
Hyper IgE Syndrome (Job)
Chronic mucocutaneous candidiasis
Which immune disorders are combined B-cell and T-cell disorders?
SCID - severe combined immunodeficiency
Which immune disorders are due to phagocyte dysfunction?
Leukocyte adhesion deficiency (Type I)
Chediak-Higashi syndrome (MT fn)
Chronic granulomatous dz (NADPH oxidase deficiency)
Which immunodeficiencies are X-linked?
Chronic Granuolmatous Dz (sometimes X-linked, not always)
Also one of the 3 types of Hyper-IgM Syndrome is X-linked (the type with no CD ligand)
What are the 3 types of Hyper-IgM syndrome?
Hyper-IgM = lots of IgM but low amts of other Ig's.
1. X-linked (no CD ligand)
2. Autosomal Recessive (no CD40)
3. NEMO deficiency
What is the defect in Bruton's agammaglobulinemia?
X-linked recessive, so moreso in Boys (one of the WBC X-linked)
Defect in BTK, a tyrosine kinase gene --> blocks Bcell differentiation and maturation --> low levels of all Ig's.
Px of Bruton's agammaglobulinemia
Recurrent bacterial infections after 6 months (decreased maternal IgG) due to opsonization defect.
Low levels of all Ig's so get lots of infections.
Labs for Bruton's agammaglobulinemia
Decreased maturation, # of B cells
Decreased Ig of all classes
Defect in Hyper-IgM syndrome
Defective CD40L on Thelper cells --> inability of B cells to class switch because need CD40-CD40L binding to signal it. So, all Ig's are stuck as IgM
Px of Hyper IgM syndrome
Severe pyogenic infections early in life.
Labs for Hyper IgM
Lots of IgM
very low IgG, IgA, IgE
No CD40L on flow cytometry for Tcells
Defect in Selective Ig Deficiency
Defect in isotype switching --> deficiency in a specific class of immunoglobulins. (Can be any, but IgA deficiency most common)
Px of Selective Ig Deficiency
Most pts are healthy, may not know.
Milk allergies and diarrhea
Assocd w atopy (allergy predisposition), asthma
Imp: Anaphylaxis on exposure to blood products with IgA.
Occurs in 1/600 pts of European descent
Labs for Selective Ig Deficiency
IgA deficiency is most common.
Failure to mature into plasma cells.
Decreased secretory IgA.
Defect in CVID (common variable immunodeficiency)
Defect in B cell maturation.
D/t many causes
Px of CVID
Can by acquired in 20s-30s
Increased risk of autoimmune dz, lymphoma, sinopulmonary infections.
Labs for CVID
Normal number of B cells but decreased plasma cells and Ig
Defect in DiGeorge Syndrome (thymic aplasia)
failure to develop 3rd and 4th brachial pouches
No Thymus - no mature Tcells = recurrent viral, protozoal, fungal infections
No Parathyroid - no PTH - low Ca2+ = tetany
Congenital heart and great vessel defects
Facial abn - cleft palate, low ears, smooth phitrum, micrognathia (chin)
No thymus, parathyroid, so decreased T cells, decreased PTH, decreased Ca2+
No thymic shadow on CXR
What are the 2 signs for low Ca2+?
Chovstek's sign- tap cheek- when facial nerve is tapped, facial muscles will contract (tetany)
Trosseau's sign- Carpal spasm when tighten BP cuff (tetany)
Defect, Px, Labs in IL-12 receptor deficiency
Defect: Decreased Th1 response
Px: Disseminated mycobacterial infections
Labs: Decreased IFN-gamma (bc Th1 are not secreting it)
Defect in Job's Syndrome (Hyper IgE)
Th cells fail to produce IFN-gamma
So PMNs (neutrophils) don't respond to chemotactic stimuli (C5a, LTB4, IL-8)
Px of Job's syndrome (IgE)
Recurrent cold abscesses (S. aureus)
Course facial features: broad nose, frontal bossing of forehead, deep eyes, doughy skin.
Also can have retained primary teeth- 2 rows of teeth!
Job was FATED:
Abcesses (cold- noninflamed)
What is the defect, Px, and Rx for chronic mucocutaneous Candidiasis?
Defect: Tcell dysfn
C. albicans infections of skin and mucous mbr
Rx: Ketoconazole (anti-fungal)
What is the defect in SCID?
Defect is in early stem cell differentiation (No Bcells, Tcells)
Can be caused by >7 diff gene defects.
Adenosine deaminase deficiency (purine salvage pathway)
Defective IL-2 receptor (X-linked defect)
Failure to synth MHC-II Ag
Only defense is NK cells.
Px of SCID
1. Recurrent infections- viral, bacterial, fungal, protozoal due to both B and T cell deficiency (chonic mucocutaneous candida, RSV, VZV, HSV, measles, flu, parainfluenza, PCP pneumonia)
2. Chronic diarrhea
Plus no thymus on CXR (like DiGeorge)
Rx for SCID
Bone marrow txplt (no allograft rejection)
Labs for SCID
Decreased IL-2R (decreased Tcell activation)
Increased adenine (toxic to B and T cells)- decreased dNTPs, decreased DNA synth.
What is ADA deficiency (Adenosine deaminase)
ADA converts Adenosine to Inosine in the purine salvage pathway.
Defective ADA means accumulation of deoxyadenosine, which leads to excess ATP and dATP. This causes imbalance in nucleotide pool, d/t fdbk inhibition of ribonucleotide reductase. This prevents DNA synth and therefore decreases lymphocyte count.
Mjr cause of SCID.
What is the defect in Ataxia-Telangiectasia?
Defect in DNA repair enz and IgA deficiency.
Px of Ataxia-Telangiectasia
1. Cerebellar defects (ataxia) plus poor smooth pursuit of moving target w eyes
2. Spider angiomas (telangiectasia) when >5yo
3. IgA deficiency
Also have increased CA risk (lymphoma, acute leukemia) and radiatiion sensitivity (avoid xray)
Die at 25yo
If you see a 1 yo with poor smooth pursuit, how should you check for Ataxia-Telangiectasia?
Increased alpha-fetoprotein (in kids >8mo)
Defect in Wiskott-Aldrich syndrome
X-linked recessive (it's an x-linked Wbc)
Progressive deletion of Bcells and Tcells
Px of Wiscott-Aldrich
Eczema (unusual bc it's trunkal eczema)
Recurrent pyrogenic infections- no IgM against capsular bacteria
Labs for Wiscott-Aldrich
High IgA, IgE
Defect in Leukocyte Adhesion Deficiency (Type 1)
Defect in LFA-integrin protein (CD18) on phagocytes. This means phagocytes can't exit circulation. (Can't "integrate" into tsu's)
Px of Leukocyte adhesion deficiency (Type I)
Recurrent bacterial infections, absent pus formation
Delayed separation of umbilicus
Labs for Leukocyte adhesion deficiency (type 1)
Neutrophilia (high amt of neutrophils in blood)
Defect in Chediak-Higashi syndrome
Defect in microtubular function with decreased phagocytosis
Defective LYST gene (lysosomal txprt)- can't get the enz which degrade things into the lysosomes.
Defective phagocyte lysosome- see giant cytoplasmic granules in PMNs (can engulf, but can't degrade once engulfed)
What is a PMN?
Polymorphonuclear Leukocytes (PMN, PML) aka granulocytes.
There are three types of granulocytes:
All have granules and lobed nuclei.
Px of Chediak-Higashi
Recurrent respi and skin infections (esp pyogenic infections by Staph and Strep)
Neurologic disorders- peripheral neuropathy
Defect in Chronic Granulomatous Dz
NADPH oxidase deficiency. Therefore phagocytes can't generate ROS (e.g. superoxide and free radicals). Absent respiratory burst in neutrophils.
Px of Chronic Granulomatous Dz
Increase susceptibility to catalase+ organisms:
Staph (esp S. aureus)
Dx of Chronic Granulomatous Dz
Nitroblue tetrazolium dye test is negative.
Normal phagocytes engulf NBT dye and oxidize it, turning it from yellow to blue-black.
Pts w CGD can't oxidize- so don't see blue-black color.
Rx for Chronic Granulomatous Dz
Prophylactic TMP-SMX (bactrin)
INF-gamma can also help.
Where is the thymus derived from embryologically?
The 3rd and 4th brachial pouches, which are ENDODERM.
What are the type of grafts (allo, auto, etc)
Autograft- from self
Syngeneic graft - from identical twin or clone
Allograft - from nonidentical pt of same species
Xenograft- from different species
What are the 4 types of txplt rejection?
What is Hyperacute rejection?
Ab-mediated (Type II HPS)
Due to presence of pre-formed anti-donor Ab in the txplt recipient.
W/in minutes after txplt
What is Acute rejection?
Tcell-mediated d/t Cytotoxic Tcells reacting against foreign MHCs.
Weeks after txplt.
Reversible with immunosuppressants
What immunosuppressants can reverse Acute Rejection?
What is Chronic rejection?
Tcell and Ab-mediated vascular dmg (obliterative vascular fibrosis)
Months-years after txplnt, Irreversible
The non-self MHC-I is seen by Cytotoxic Tcells as self MHC-I which is presenting foreign Ag, so it attacks.
Take immunosuppresants after txplt to delay this.
What is Graft-vs-Host dz?
Grafted immunocompetent Tcells proliferate in the immunocompromised host and reject foreign (to them) cells- which are the host's cells.
Causes severe organ dysfn.
Mjr sympt: maculopapular rash, jaundice hepatosplenomegaly, diarrhea.
What does the Long Thoracic N innervate
(scapular winging if lesioned)
What does the Suprascapular N. innervate?
Infraspinatus M (lateral rotator)
Supraspinatus M (1st 10degrees of arm abduction)
What does the Lateral Pectoral Nerve innervate?
Pectoralis Mjr M.
What does the Upper Subscapular N. innervate?
Subscapularis M. (medial rotator)
What does the Thoracodorsal nerve innervate?
Latissimus Dorsi M.
What does the Lower Subscapular N. innervated?
Teres Mjr M. (medial rotator, extender, ADductor)
What does the Musculocutaneous N. innervate?
What does the Axillary N. innervate?
What does the Radial N. innervate?
Extensors of forearm
What does the Median nerve innervate?
Causes Pope's blessing, Ape hand
What does the Ulnar N innervate
Causes claw hand
What is Cori's disease?
Deficiency in glycogen debranching enz.
Glycogen is stored in the liver. With debranching enz deficiency, it can't undergo glycogenolysis (glycogen breakdown) to turn it into glucose.
With no glucose except from diet, there is hypoglycemia.
This leads to FTT.