MI 05c: Hypersensitivity

Question 1

Define sensitivity.

Answer 1

Individual who’s been exposed to antigen has reaction to subsequent encounters with that antigen

Question 2

Define hypersensitivity.

Answer 2

Disorder of immune response in which sensitivity to antigen results in inappropriate/poorly controlled response (causing injury)

Question 3

Most types of hypersensitivity are primarily mediated via (X). Which type is the exception, mediated primarily by (Y)?

Answer 3

X = Ab (Types I-III)
Y = T cells (Type IV)

Question 4

Type I hypersensitivity: primarily mediated by (X) Ab, targeted against (Y).

Answer 4

X = IgE
Y = allergen

Question 5

Type (X) hypersensitivity is super fast/immediate. Type (Y) is slow.

Answer 5

X = I
Y = IV

Question 6

What are the three types of antigen, specifically (X), transmission that can cause Type I hypersensitivity?

Answer 6

X = allergen

Injected, ingested, inhales

Question 7

An individual becomes “allergic” or “atopic” to allergen due to which events taking place?

Answer 7

1. Sensitization of Th2 cells

2. High production of IgE (coat mast cells)

Question 8

A late phase allergy reaction (hours after exposure) is result of (X) release from (Y) cells.

Answer 8

X = cytokine
Y = mast

Question 9

Type I hypersensitivity: reaction involves rapid proliferation of which cells?

Answer 9

No proliferation needed! Immediate response via mast cells

Question 10

Type I hypersensitivity is characterized by vascular (dilation/constriction) and smooth muscle (contraction/relaxation).

Answer 10

Dilation;

Contraction

Question 11

Type I hypersensitivity: which mast cell mediators are pre-formed? What’s their effect?

Answer 11

1. Vasoactive amines (vasodilation)

2. Proteases (tissue damage)

Question 12

Type I hypersensitivity: which mast cell mediators are formed rapidly de novo? What’s their effect?

Answer 12

1. Prostaglandins (vasodilation)

2. Leukotrienes (smooth muscle contraction)

Question 13

T/F: All immune reactions in Immediate (Type I) hypersensitivity are immediate.

Answer 13

False

Question 14

Later phase reactions in Type I hypersensitivity include which cells?

Answer 14

Leukocytes; Influx of Th2 cells, eosinophils, neutrophils, basophils

Question 15

Allergic reaction to pollen includes which symptoms, due to which components of Type (X) hypersensitivity?

Answer 15

X = I

1. Vasodilation (histamine)
2. Mucus secretion (IL-13 from Th2)

Question 16

Asthma due to allergic reaction includes which symptoms, due to which components of Type (X) hypersensitivity?

Answer 16

X = I

1. Vasodilation (histamine)
2. Mucus secretion (IL-13 from Th2)
3. Smooth muscle contraction (leukotrienes)

Question 17

Anaphylaxis symptoms can range from mild, such as (X), to life-threatening, aka (Y).

Answer 17

X = hives
Y = anaphylactic shock

Question 18

Which complement components play role in anaphylaxis?

Answer 18

C5a, C3a, C4a

Question 19

Anaphylactic shock is technically a sudden (X), caused by (vasodilation/vasoconstriction).

Answer 19

X = fall in blood pressure

Vasodilation

Question 20

Anaphylaxis that results from penicillin allergy: penicillin acts as a(n) (X), so it’s not immunogenic. How does it cause anaphylaxis then?

Answer 20

X = hapten;

Binds to proteins to create neoepitopes (which cause Th2 response)

Question 21

Hypersensitivity Type II is known as (X)-mediated. It’s primarily mediated by (Y) Ab, targeted against (Z).

Answer 21

X = cell or Ab
Y = IgM, IgG
Z = specific tissue or cell antigens

Question 22

T/F: Hypersensitivity Type II is usually systemic.

Answer 22

False - usually targeted to particular location

Question 23

Rheumatic fever is result of Ab cross-reaction with which antigens? This is example of hypersensitivity type (X).

Answer 23

X = II

Streptococcal cell wall antigen and myocardial antigen (resulting in myocarditis)

Question 24

In myasthenia gravis, (X) targets and (Y), thus (stimulating/inhibiting) (Z). This is example of hypersensitivity type (I/II/III/IV).

Answer 24

X = Ab
Y = ACh receptor
Inhibiting
Z = ACh binding

Type II

Question 25

Immunofluorescence image depicts targeted depots of (X) Ab along glomerular basement membrane. Which hypersensitivity type (I/II/III/IV) disease do you suspect?

Answer 25

X = anti-GBM (glomerular basement membrane) Ab Type II Goodpasture's syndrome

Question 26

T/F: Hypersensitivity Type III is usually systemic.

Answer 26

True

Question 27

Hypersensitivity Type III is known as (X)-mediated. There are characteristic (Y) deposits in (Z) locations.

Answer 27

``` X = Y = immune complex Z = blood vessels ```

Question 28

The central issue in Hypersensitivity Type III is that (X) are less efficient at fixing (Y).

Answer 28

``` X = small immune complexes Y = complement and deposit in blood vessel walls ```

Question 29

Hypersensitivity Type III: (X) produce (Y) through complement activation. Then (Y) cause (Z), which causes hives.

Answer 29

``` X = small immune complexes Y = C3a and C5a Z = histamine release from mast cells ```

Question 30

Hemorrhaging in skin is characteristic of hypersensitivity type (X). Describe mechanism behind these hemorrhages.

Answer 30

X = III Platelets accumulate around site of immune-complex deposition and form clots that cause blood vessels to burst

Question 31

If you had to name the key culprit behind hypersensitivity type III symptoms, it would be (Ag/Ig).

Answer 31

Ag:Ig interaction (immune complex)!

Question 32

In type (X) hypersensitivity, a therapy strategy would be to block FcR, since injury is caused by Fc-mediated (Y).

Answer 32

``` X = III Y = inflammation ```

Question 33

Hypersensitivity Type (X) reaction is relatively slow, occuring (Y) hours after contact with antigen. What's taking so long?

Answer 33

``` X = IV Y = 24-72 (1-3 days) ``` Antigen presentation, recognition, activation, differentiation, trafficking of T cells

Question 34

Most Hypersensitivity Type III reactions mediated specifically by (X).

Answer 34

X = Th1 cells and CTL

Question 35

T cell response in Type (X) hypersensitivity results in production of which specific cytokines? What's the effect of each?

Answer 35

X = IV 1. Chemokines (leukocyte recruitment) 2. IFN-gamma (macrophage activation) 3. TNF-alpha (local tissue destruction)

Question 36

List three key autoimmune diseases dominated by effector T cells.

Answer 36

1. MS 2. Rheumatoid arthritis 3. Type I diabetes mellitus

Question 37

T/F: Crohn's disease is autoimmune.

Answer 37

False

Question 38

(X) are believed to be dominant contributor to tissue injury in many autoimmune diseases.

Answer 38

X = T cells

Question 39

Anti-TNF Ab is a good therapy strategy for (X)-mediated diseases, aka Type (Y) hypersensitivity.

Answer 39

``` X = T cell Y = IV ```