Hypersensitivities

Question 1

outline the 4 hypersensitivites

Answer 1

1. Immediate hypersensitivity/Type I: IgE, mast cells and lipid mediators.2. Antibody mediated/Type II:IgM and IgG against cell-bound or extracellular matrix Ag.3. Immune complex/Type III:IgM and IgG immune complex deposition.4. Delayed Type Hypersensitivity/Type IV:CD4 mediated delayed type hypersensitivity.

Question 2

cells and antibody involved in type 1

Answer 2

Th2, mast, eosinophils, IgE

Question 3

MOA of type 1 hypersensitivty

Answer 3

Allergen causes APC (which can be a basophil) to secrete IL-33 which gets Basophils to secrete IL-4. => IL-4 causes differentiation to TH2 => induces B cell isotope switching to IgE = > IgE binds to Mast cells which immediate release histamine (early response - Wheal and Flare) => eventually release cytokines (late response) which attracts leukocytes, eps. Eosinophils (whose regulation is bypassed in allergy)

Question 4

activation of a mast cell results in (3)?

Answer 4

1. Secretion of preformed mediators (30-45 secs) - eg. histamine.2. Synthesis and secretion of lipid mediators (10 -30 min) -prostaglandins and leukotrienes.3. Synthesis and secretion of cytokines (slow) - IL-3, IL-4, Il-5.

Question 5

cell involved in type 4?

Answer 5

TH1

Question 6

guve 3 examples of type 4 . explain each

Answer 6

1. Contact sensitivity – (poison ivy)• Previous sensitization, upon re-exposure central and effector memory cells are triggered.2. Mycobacterium tuberculosis• Inability to clear organism results in persistentactivation of TH1 T cells.3. Celiac Disease• Exposure to wheat products induces TH1 dependentimmunopathology of intestinal wall.

Question 7

what is a type II hypersensitivity in one sentence

Answer 7

antibodies (IgM or IgG) bind to self antigens, these can be cell bound or part of the ECM.

Question 8

What are the 2 outcomes of a type II hypersensitivity?

Answer 8

1. injury due to immunological mediators.2. Abnormal physiological response by binding to receptors (can stimulate or inhibit)

Question 9

give examples for each type of outcome in a type 2 hypersensitivity

Answer 9

1 . injury due to immunological mediators. - in a blood transfusion there may be antibodies to erythrocytes.2. Abnormal physiological response - Graves disease produces stimulatory antibodies. Myasthaenia Gravia produces inhibitory antibodes

Question 10

in a type 3 hypersensitivity what are the immune complexes made of?

Answer 10

can either be self or foreign antigen. Bounded to antibodies

Question 11

give 3 reasons why immune complexes may persist in ciruclation

Answer 11

excess antigen, low afinity antibodies, inefficient complement activation

Question 12

3 most common places for immune complexes to deposit

Answer 12

kidneys, vessels and joints

Question 13

classic example of type 3 disease

Answer 13

SLE