Hypersensitivity Reactions

Question 1

What happens in Type-1 Hypersensitivity Reactions?

Answer 1

Anaphylactic, immediate

IgE-mediated! –> histamine release (bee sting, hay fever, asthma)

Question 2

What happens in Type-II Hypersensitivity Reactions?

Answer 2

Antibody-dependent cytotoxicity

Antibody attaches to cell bearing corresponding antigen –> cell death

Ex. transfusion reaction, autoimmune hemolytic anemia, hashimotos, good pasture’s disease

Question 3

What happens in Type-III Hypersensitivity Reactions?

Answer 3

Immune complex

Formation of large immune complexes not cleared by phagocytosis

Ex. rheumatoid arthritis, systemic lupus erythematosus

Question 4

What happens in Type-IV Hypersensitivity Reactions?

Answer 4

Delayed (>12 hours to develop)

Sensitized T cells release interleukins –> monocyte & lymphocyte infiltration

Ex. contact dermatitis (poison ivy, chemicals), TB, leprosy, graph vs host