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Mircobiology > Exam 4 > Flashcards

Exam 4 Flashcards

1
Q

Describe an antigen

A

Molecules that can be seen and identified by the immune system.

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2
Q

Describe an epitope

A

The actual binding site of the immunogen is so specific it only binds this portion of the molecule

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3
Q

Describe what the MHC is

A

Major histocompatibility complex: one of the set of genes that codes for human cell markers or receptors.
Gives rise to a series of glycoproteins found on all cells except RBC.
Also known as the human leukocyte antigen (HLA) system.
These markers play a vital role in recognition of self by the immune system and in rejections of foreign tissue.

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4
Q

What are the 3 major functions of activated T cells

A

Helper T cells: activate macrophages, assist B-cell processes, and help activate cytotoxic T cells.
Regulatory T cells: control T-cell response by secreting anti-inflammatory cytokines or preventing proliferation
Cytotoxic T cells: lead to the destruction of infected host cells and other “foreign” cells

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5
Q

Describe the two most common functions of activated B-cells

A

Plasma cells: release antibodies into the tissue and the blood
Antibodies: attach to the antigen for which they are specific, and the antigen is marked for destruction or neutralization.

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6
Q

List the function of CD3 receptors and where they’re found

A

Surround T-cell receptors and assist in binding

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7
Q

List the function of CD4 receptors and where they’re found

A

Accessory receptor proteins that helps the T-cell receptor bind to MCH II molecules

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8
Q

List the function of CD8 receptors and where they’re found

A

found on cytotoxic T-cells and helps bind MCH I molecules (kills infected self)

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9
Q

Contrast B and T cells

A

B-cells: develop in the bone marrow. immunoglobulin is the specific surface marker, low numbers circulating in the blood, b-cell receptor (immunoglobulin), distribution in lymphatic organs is in cortex (follicles) doesn’t require an antigen presented produces plasma cells and memory cells, general functions produces antibodies to inactivate, neutralize, target antigens.

T-cells: develop in the thymus, specific surface markers are t-cell receptor & several CD molecules, high numbers in the blood stream, receptor for antigens in the T-cell receptor, distribution in lymphatic organs is in paracortical sites (interior to the follicles) needs an antigen presented, produces several types of T-cells and memory cells general functions cells activated to help other immune cells; suppress or kill abnormal cells; mediate hypersensitivity; synthesize cytokines

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10
Q

Describe the structure of immunoglobulin

A

Large glycoprotein molecules that serve as the antigen receptors of B-cells. Serves as antibodies when secreted.
Looks like a font Y has pockets in the ends of forks of the molecules that can be highly variable in shape to fit a wide range of antigens, has areas of extreme versatility from one clone to another. Has light chain (right top) heavy chains (right bottom) Variable region (top left)

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11
Q

Describe the structure of an antibody

A

every antibody is unique

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12
Q

Describe the process that results in the incredible diversity of IG/antibody and T-cell receptor diversity and specificity

A

Diversity is generated by rearrangement of gene segments that code for antigen receptors on T and B cells every possible recombination occurs, leading to a huge assortment of lymphocytes
It is estimated that each human produces antibodies with 10 trillion different specificities

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13
Q

What is clonal selection

A

The mechanism by which the exactly correct B or T cell is activated by any incoming antigen. Lymphocyte specificity is preprogrammed, existing in the genetic makeup before an antigen has ever entered the tissues. Each genetically distinct lymphocyte expresses only a single specificity and can react to that chemical epitope

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14
Q

What is clonal expansion

A

The rapid multiplication of B or T cell clones after activation by an antigen

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15
Q

What is clonal deletion

A

The process by which any such clones are destroyed during development

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16
Q

Describe the characteristics of a “good” antigen

A

a) their chemical composition (complex, not repeated); b) their context (meaning what types of cytokines are present); and c) their size:

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17
Q

Define Hapten

A

Small foreign molecules that are too small by themselves to elicit an immune response
If this incomplete molecule is linked to a larger carrier molecule, the combination develops immunogenicity
The hapten serves as the epitope

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18
Q

Describe what superantigens are and what can result in people who react to them

A

Bacterial toxins that are potent stimuli for T cells
Activate T cells at a rate 100 times greater than ordinary antigens
The result can be an overwhelming release of cytokines and cell death
Toxic shock syndrome and certain autoimmune diseases are associated with superantigens

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19
Q

Describe the process of antigen presentation by dendritic cells, including the MHC and CD proteins involved in the process, what they present to, and the result of presentation​

A

In most immune reactions, the antigen must be formally presented to lymphocytes by antigen-presenting cells (APCs)
Examples of APCs:
Macrophages
B cells
Dendritic cells (usually these)
After processing is complete, the antigen is bound to the MHC receptor and moved to the surface of the APC so it will be readily accessible to T lymphocytes

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20
Q

Know whether all antigens must use APCs to lead to B-cell activation

A

Most antigens must be presented first to T cells, even though they will eventually activate both the T-cell and B-cell systems
T-cell-independent antigens: antigens that can trigger B cells directly without APCs or T helper cell

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21
Q

Describe the process of B cell activation

A

a precomitted B cell binds to the epitope of the receptor
The anitgen is endocytosed by the B cell and degraded into smaller pieces and bound to the MHC-II receptors on the surface of the B cell. For most B-cells to become functional, the must interact with an already active helper T-cell that bears receptors for antigen from the same microbe. This T cell has also been activated by an APC. The two cells enlarge in linked recognition, in which the NHC-II receptor bearing antigen on the B-cell binds to the T-cell antigen receptor, the CD3 Molecule, and the CD4 molecule on the T-cell. The combination of these stimuli on the membrane receptors causes a signal to be transmitted internally to the B-cell nucleus. This event triggers B-cell activation. The B-cell now differentiates into 3 types of B-cells: plasma cells, memory cells, and regulatory cells. Each of the 3 cells expand it’s population. Plasma cells are short lived factories for antibodies of the same specificity as the original B-cell. Memory cells seed the lymphatic circulation, ready for encounters with the same antigens. Regulatory cells proliferate and secrete IL-10 to regulate T-cell response.

22
Q

List the 6 different functions of an antigen

A

Opsonization: a process that makes microbes readily recognized by phagocytes, which dispose of them.

Neutralization: Anitbodies fill the surface receptors on the virus or the active site on a microbial enzyme to prevent it from attaching normally.

Agglutinate: the result of antigens cross-linking their cells into large clumps, which renders the antigen immobile and enhances their phagocytosis.

Complement: the interaction of an antibody w/ complement can result in specific rupturing of cells in some viruses.

Antitoxin: a special type of antibody that neutralizes bacterial toxins.

23
Q

Define titer

A

the concentration of an anitbody

24
Q

Describe the pattern of primary and secondary immune system response to antigen in terms of titer over time

A

In the primary response after the latent period there is an increase of the serum titer to a plateau then tapers off to a low level after weeks and months.

In the secondary response the titer is greatly increased over the primary response.

25
Q

Describe active immunity

A

Occurs when an individual receives immune stimulus that activates B and T cells to produce immune substances such as antibodies

Creates memory that renders the person ready for quick action upon reexposure to the same antigen

Requires several days to develop

Lasts for a relatively long time

Can be stimulated by natural or artificial means

26
Q

Describe passive immunity

A

Occurs when an individual receives antibodies from another human or animal

Recipient is protected for a short period of time, even though they have not had prior exposure to the antigen

Lack of memory for the original antigen

Lack of antibody production against the disease
Immediate onset of protection

Short-term effectiveness
Can be natural or artificial in origin

27
Q

Describe natural immunity

A

any immunity that is acquired through the normal biological experiences of an individual

28
Q

Describe artificial immunity

A

protection from infection obtained through medical procedures such as vaccines and immune serum

29
Q

Describe a whole cell vaccine

A

Live, attenuated cells or viruses

Killed cells or inactivated viruses

30
Q

Describe a subunit vaccine

A

Subunits derived from cultures of cells or viruses
Subunits synthesized to mimic natural molecules found on pathogens
Subunits manufactured via genetic engineering

31
Q

Describe why an attenuated microbe is safe for vaccination

A

Because the microbes virulence is reduced. Allowing the immune system to create antibodies against the microbe without endangering the host.

32
Q

Describe what an adjuvant is and why it is used in a vaccine

A

Special binding substance required by some vaccines:
Enhances immunogenicity
Prolongs antigen retention at the injection site
Precipitates the antigen and holds it in the tissues so that it will be released gradually
Facilitates contact with antigen-presenting cells and lymphocytes
Most common adjuvant is alum (aluminum hydroxide salts)

33
Q

Describe what herd immunity is and why it is important in terms of vaccination

A

Not everyone can be vaccinated, but the resistance to the spread of a contagious disease within a population that results if a sufficiently high proportion of individuals are immune to the disease, especially through vaccination.

34
Q

List the common side effects of a vaccination

A

Local reactions at the injection site
Fever
Allergies
Other adverse outcomes

35
Q

Know the symptoms, transmission, virulence factors and treatment of Staphylococcus aureus MRSA

A

Methicillin-resistant Staphylococcus aureus (MRSA)
Symptoms: Raised, red, tender, localized lesions
Features pus and feels hot to the touch
Transmission: Contaminant of all kinds of surfaces: gym equipment, airplane tray tables, electronic devices, razors, etc
Virulence factors: Coagulase is a diagnostic species characteristic
Also produce hyaluronidase, staphylokinase, DNase, and lipase
Treatment: Prevention is only possible with good hygiene
Treatment through incision of lesion and pus drainage
Antimicrobial treatment should include more than one antibiotic (vancomycin is recommended in U.S.)

36
Q

Know what a maculopapular rash is

A

Skin eruptions caused by a variety of microbes

Flat to slightly raised colored bumps (skin color is important but often has been too rarely characterized)

37
Q

Know the causative agent, symptoms, transmission, virulence factors and treatment of measles

A

Symptoms: Sore throat
Dry cough
Headache
Conjunctivitis
Lymphadenitis
Fever
Oral lesions
Virulence Factors: Virus implants on respiratory mucosa and infects the tracheal and bronchial cells
It travels to the lymphatic system where it multiplies and enters the bloodstream (viremia) which carries the virus to the skin and various organs
Cell membranes of adjacent host cells fuse into large syncytia (giant cells with many nuclei) and no longer perform their proper function
Transmission: Transmitted by respiratory droplets
Humans are the only reservoir
Causative Agent: Morbillivirus
Treatment: Reducing fever
Suppressing cough
Replacing lost fluid
Remedies to relieve neurological and respiratory symptoms and to sustain nutrient, electrolyte, and fluid levels
Vitamin A supplements are recommended

38
Q

Know the causative agent, symptoms, transmission, virulence factors and treatment of rubella

A

Symptoms: rash
Causative agent: Rubivirus
Virulence factors: Virus has the ability to stop mitosis, an important process for a developing embryo and fetus. Induces apoptosis of normal tissue cells, causing irreversible harm to organs. Damages vascular endothelium, leading to poor development of many organs
Treatment: Vaccine
Transmission: Initiated through contact with respiratory secretions and occasionally urine

39
Q

Know the causative agent, symptoms, transmission, virulence factors and treatment of roseola

A

Symptoms: Can result in a maculopapular rash, Usually accompanied by a high fever (41°C or 105°F) that comes on quickly and lasts up to 3 days. Seizures may occur during this period.
On the fourth day, the fever disappears and the rash appears, first on chest and trunk, then less prominently on the faceand limbs
Causative Agent: Human herpesvirus 6
Transmission: It is thought that 100% of the U.S. population is infected with the virus by adulthood
Treatment: No vaccine and no treatment exist for roseola

40
Q

Know the causative agent, symptoms, transmission, virulence factors and treatment of chicken pox/Shingles

A

Symptoms: Fever and abundant rash appear after an incubation period of 10 to 20 days: rash begins on the scalp, face, and trunk, and radiates in sparse crops to the extremities
Skin lesions progress quickly from macules and papules to itchy vesicles filled with a clear fluid. Encrust and drop off after several days; heal completely or may leave a small scar Lesions can number from a few to hundreds; more abundant in adolescents and adults
Transmission: Humans are a natural host fro HHV-3. Harbored in the respiratory droplets and fluid from active lesions
Virulence Factors: HHV-3 enters the respiratory tract, attaches to respiratory mucosa, and invades and enters the bloodstream. Viremia disseminates the virus to the skin, where it causes adjacent cells to fuse and lyse, causing characteristic lesions. The virus then enters sensory nerves and dorsal root ganglia. Ability to remain latent in nerve ganglia is an important virulence factor
Causative Agent: HHV 3

41
Q

Know the causative agent, symptoms, transmission, virulence factors and treatment of Ringworm

A

Symptoms: a ring under the skin
Causative agent: Trichophyton, Microsporum, and Epidermophyton
virulence factors: Dermatophytes have the ability to digest keratin. Fungi do not invade deeper epidermal layers
Transmission: Direct contact and indirect contact with other humans or infected animals
Treatment: Therapy is a topical, antifungal ointment applied for several weeks. Several drugs work by speeding up loss of the outer skin layer

42
Q

Know the causative agent, symptoms, transmission, virulence factors and treatment of conjuctivitis

A

Symptoms: Most bacterial infections produce a milky discharge. Viral infections produce a clear, watery exudate. Patients often wake up in the morning with the eye “glued” shut by secretions that have accumulated and solidified overnight. Some conjunctivitis cases are caused by an allergic response and a clear, watery fluid is formed. Common name is pinkeye
Transmission: Transmitted vertically from a genital tract infection in the mother
Causative Agent: Neisseria gonorrhoeae or Chlamydia trachomatis
Treatment: Ciprofloxacin is a common choice because it covers all possible bacterial infections. Physicians may prescribe prophylactic antibiotic eye drops even if a viral case is suspected

43
Q

Describe the meninges of the nervous system

A

the three membranes (the dura mater, arachnoid, and pia mater) that line the skull and vertebral canal and enclose the brain and spinal cord.

44
Q

Describe the blood-brain barrier and normal microbiota of the CNS

A

Vascular interface between the blood vessels serving the brain and the brain itself. Cells that make up the walls of these blood vessels allow very few molecules to pass through. Prohibits most microorganisms and most antibiotics from entering the nervous system. Therefore the CNS has no normal microbiota

45
Q

Describe what the term meningitis refers to

A

Inflammation of the meninges.

46
Q

Describe the symptoms of general meningitis

A

Symptoms: Severe headache
Painful or stiff neck
Fever
Nausea and vomiting
Photophobia (sensitivity to light)
Skin rashes may be present in specific types of meningitis.
Increased number of lymphocytes in the CSF

47
Q

Know the virulence factors, symptoms, transmission and treatment for meningitis caused by Neisseria

A

Symptoms: Sudden onset of disease
Fever higher than 40°C or 104°F
Sore throat
Chills
Delirium
Widespread areas of bleeding under the skin
Shock
Coma
Generalized intravascular clotting
Cardiac failure
Damage to the adrenal glands
Death within a few hours
Virulence Factors: Bacteria enters the body via the upper respiratory tract, moves into the blood, rapidly penetrates the meninges, and produce symptoms
Pathogen releases endotoxin into the generalized circulation, which stimulates white blood cells
Damage to the blood vessels caused by cytokines leads to vascular collapse, hemorrhage, and petechiae on the trunk and appendages
Transmission: Usually acquired through close contact with secretions or droplets
Treatment: Vital that antibiotic therapy begin as soon as possible. High doses of penicillin G given intravenously. Treatment for shock and intravascular clotting may also be required

48
Q

Know the virulence factors, symptoms, transmission and treatment for meningitis caused by Streptococcus pneumoniae

A

Virulence factors: Has a polysaccharide capsule that protects it against phagocytosis. Produces an alpha-hemolysin and hydrogen peroxide that damage the CNS. Capable of inducing brain cell apoptosis. Can penetrate the respiratory mucosa, gain access to the bloodstream, and enter the meninges
Treatment: Vaccines and antibiotics

49
Q

Know the virulence factors, symptoms, transmission and treatment for meningitis caused by Listeria monocytogenes

A

virulence factors: Not fastidious: resistant to cold, heat, salt, pH extremes, and bile. Grows inside host cells and can move directly from an infected host cell to an adjacent healthy cell
Symptoms: Mild or subclinical infection in healthy adults, including nonspecific symptoms of fever, diarrhea, and sore throat
Transmission: Reservoir is soil and water. Animals, plants, and food are secondary sources of infection. Most cases of listeriosis are associated with ingesting contaminated dairy products, poultry, and meat
Treatment: Antibiotic therapy should be started as soon as listeriosis is suspected

50
Q

Know the virulence factors, symptoms, transmission and treatment for meningitis caused by Cryptococcus neoformans

A

Symptoms: Causes a chronic form of meningitis with a gradual onset of symptoms. Onset may be fast in AIDS patients and the disease is more acute. Sometimes classified as meningoencephalitis. Headache most common symptom. Nausea and neck stiffness also common
Transmission: Primary ecological niche is the bird population. Present in urban areas where pigeons congregate. Proliferates in high-nitrogen environment of bird droppings. Masses of dried yeast cells are scattered into the air and dust. Healthy humans have a strong resistance to it
Highest rates of infection occur in patients with AIDS. Frequently fatal
Steroid treatment, diabetes, and cancer also predispose individuals to infection

51
Q

Know the virulence factors, symptoms, transmission and treatment for meningitis caused by Coccidiodes

A

Virulence factors: True systemic fungal infection of high virulence. Begins as a pulmonary infection, but can disseminate throughout the body. Coccidioidomycosis of the meninges is the most serious manifestation. All persons inhaling arthrospores probably develop some degree of infection, but some have a genetic susceptibility that gives rise to more serious disease. Arthrospores develop into spherules in the lungs. Mild respiratory systems can develop into disseminated disease, including meningitis, osteomyelitis, and skin granulomas
Transmission: Outbreaks are usually associated with farming activity, archeological digs, construction, and mining

Mircobiology (3 decks)

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