Type IV Immunopathology

Question 1

Define type IV immunopathology.

Answer 1

(n.) a form of autoimmunity mediated by T cells; formerly called delayed-type hypersensitivity; does not require antibody or B cells

Question 2

Explain why a person usually has no observed symptoms when first exposed to a “contact sensitizer” like poison ivy.

Answer 2

Poison ivy irritation is a delayed-type hypersensitivity reaction, so one needs prior exposure to generate memory cells.

Question 3

Explain the difference between initiation and elicitation.

Answer 3

Initiation creates memory T cells and elicitation excites those cells into action – generating angry macrophages.

Question 4

______, and not Th1, would be the predominate cell in a positive PPD at 48 hours.

Answer 4

Macrophages (because Th1 cells can stimulate 1,000 macrophages)

Question 5

What does abacavir do in 8% of patients?

Answer 5

Changes the HLA B5701 (an MHC I) shape, causing CTLs to attack.

Question 6

Hyperacute reactions occur when _________.

Answer 6

the host develops antibodies to the graft’s MHC