Immune responses Flashcards Preview

Boards > Immune responses > Flashcards

Flashcards in Immune responses Deck (11):
1

What causes a Type I hypersensitivity reaction?

Free antigen cross-links IgE on presensitized mast cells or basophils

An immediate histamine reaction followed by a delayed leukotriene reaction

2

What causes a Type II hypersensitivity reaction?

An antibody (IgM or IgG) mediated cytotoxic event

(think autoimmune to a specific tissue or site where antigen is found)

3

What is a direct Coombs' test?

Detects antibodies that HAVE adhered to PATIENT'S RBCs

(tests an Rh+ infant of an Rh- mother)

4

What is an indirect Coombs' test?

Detects antibodies that CAN adhere to OTHER'S RBCs

(tests an Rh- woman for Rh+ antibodies)

5

What causes a Type III hypersensitivity reaction?

A complex of 3 things (Ag-Ab-complement)...activated complement attracts neutrophils...which come in and release lysosomal enzymes

(think vasculitis and systemic manifestations)

6

What causes a Type IV hypersensitivity reaction?

Sensitized T cells encounter antigen and release lymphokines...leads to macrophage activation (delayed hypersensitivity)

(NO antibodies)

7

What is an autograft? Syngenic graft? Allograft? Xenograft?

Autograft...from self
Syngenic graft...from identical twin (or clone)
Allograft...from nonidentical individual of same species
Xenograft...from different species

8

Transplant rejection happens within minutes. What kind of reaction is it?

Hyperacute.

Type II reaction...pre-existing antibodies react to donor antigen

9

Transplant rejection happens after weeks-months. What kind of reaction is this

Acute.

Cellular: CTLs activated against donor MHCs
Humoral: Antibodies develop after transplant (so unlike hyperacute)

10

Transplant rejection happens after months-years. What kind of reaction is this?

Chronic.

Recipient T cells perceive donor MHC as recipient MHC (so unlike acute); however, T cells react against donor antigens presented...both cellular and humoral components

11

What happens with GVHD?

Grafted immunocompetent T cells proliferate in immunocompromised host and reject HOST cells