Immuno - hypersensitivity

Question 1

Anaphylactic hypersensitivity

Answer 1

Type I

free antigen cross-links IgE, triggers mast cell and basophil degranulation (delayed response = leukotrienes)

First and Fast

Test: skin test for specific IgE

Question 2

Cytotoxic hypersensitivity

Answer 2

Type II - cy-two-toxic

IgM/IgG bind antigen on foreign cell, tag for destruction (phagocytosis, complement-mediated inflammation, Ab-mediated cellular dysfunction)

Direct Coombs’: detect antibodies that have adhered to RBCs
Indirect Coombs’: detect free serum antibodies that can adhere to RBCs

Question 3

Immune complex mediated hypersensitivity

Answer 3

Type III (3 things! Antigen - antibody - complement)

Immune complex attract neutrophils, which release lysosomal enzymes

serum sickness - 5 days post-exposure, deposition of complexes in membranes leading to tissue damage. Now commonly caused by drugs, look for fever, urticaria, arthralgia, etc.

Arthus reaction - local subacute rxn after intradermal injection of antigen. Look for edema, necrosis, activation of complement

Question 4

T-cell mediated hypersensitivity

Answer 4

Type IV - delayed

4 T’s: T cells, Transplant rejection, TB skin test, Touching

Sensitized T cells release cytokines after stimulation by antigen. No antibodies involved!

Question 5

I: Allergic/atopic disorders, anaphylaxis

Answer 5

Type I Anaphylactic hypersensitivity

Question 6

II: antibody mediated hemolysis, Goodpasture, Graves, GB syndrome, ITP, MG, rheumatic fever

Answer 6

Type II Cytotoxic hypersensitivity

Question 7

III: Arthus rxn, SLE, polyarteritis nodosa, PSGN (vasculitidies)

Answer 7

Type III Immune complex mediated hypersensitivity

Question 8

IV: Contact derm, GVHD, MS, PPD (no antibodies!)

Answer 8

Type IV T-cell mediated hypersensitivity

Question 9

Blood transfusion followed by urticaria, wheezing, fever

Answer 9

Allergic - Type I against plasma proteins

Question 10

Blood transfusion followed by dyspnea, bronchospasm

Answer 10

Anaphylaxis - severe allergic rxn (breathing problems)

Question 11

Blood transfusion followed by fever, headaches, chills, flushing

Answer 11

Febrile non-hemolytic - Type II, host antibodies against donor HLA antigens and WBCs

Question 12

Blood transfusion followed by fever, hypotension, hemoglobinuria, jaundice

Answer 12

Acute hemolytic - Type II, intravascular/ABO incompatibility (hemoglobinuria) or extravascular/host antibody rxn (jaundice)