Hypersensitivity Basics

Question 1

Type I (description & test)

Answer 1

Anaphylactic/atopic (free antigen cross-links IgE on presensitized mast cells and basophils - triggering release of vasoactive amines)

Test: scratch test and radioimmunosorbent assay

Question 2

Type II (description & test)

Answer 2

Antibody mediated - CYTOTOXIC

Test: direct and indirect Coombs

Question 3

Type III (description & test)

Answer 3

IMMUNE COMPLEX

Test: immunofluorescent staining

Question 4

Type IV (description & test)

Answer 4

DELAYED (T-cell mediated) type - sensitized T-lymphocytes encounter antigen and then release lymphokines (leading to macrophage activation - NO ANTIBODY INVOLVED!)

Test: patch test (i.e. PPD)

Question 5

Examples of Type I HSR

Answer 5

Anaphylaxis (i.e. bee sting/food allergies etc), allergic/atopic disorders (hay fever)

Question 6

Examples of Type II HSR

Answer 6

Hemolytic anemia, pernicious anemia, ITP, erythroblastosis fetalis, acute hemolytic transfusion reactions, rheumatic fever, goodpasture’s, bullous pemphigoid, pemphigus vulgaris, graves disease, myastenia gravis

Question 7

Examples of Type III HSR

Answer 7

SLE, RA, polyarteritis nodosum, poststreptococcal glomerulonephritis, serum sickness, arthus reaction (i.e. swelling/ inflammation following tetanus vaccine), hypersensitivity pneumonitis (i.e. farmer’s lung)

Question 8

Examples of Type IV HSR

Answer 8

DM1, MS, guillain-barre, hasimoto’s thyroiditis, graft-vs-host disease, PPD test, contact dermatitis (i.e. poison ivy)