Type III & IV hypersensitivity & autoimmunity

Question 1

Type III H aka

Answer 1

Immune complex hypersensitivity or clumping

I=acId or C=abCd

Question 2

how does Type III H work?

Answer 2

Ab+Ag forms AgAb (immune complex) and it is deposited

• usually deposited on endothelium d/t slow flow such as in kidneys (glomerulonephritis)
• when it attaches the complement and basophils and neutrophils will remove it which leads to damage
• inflammation and tissue damage follows

Question 3

examples of Type III H

Answer 3

glomeulonephritis and rheumatoid arthritis
-in rheumatoid arthritis the immune complex deposits in joints and inflammation is caused when the IC is removed by complement as it damages not only the IC but also whatever cell it is attached to

Question 4

Type III Immune COmplex H (._______?) why is this word used?

Answer 4

clumping

• clumps form when we make enough Ab to bind to the Ag but not enough Ab to get rid of the Ag
• these clumps cause problems when they settle in joints or the small blood vessels in the kidney

Question 5

2 reasons why immune complex isnt removed during Type III H

Answer 5

1-some are insoluble

2-not recognized by enzymes (too small)

Question 6

Type IV aka

Answer 6

T cell mediated H OR delayed H

Question 7

Type IV H is mediated by

Answer 7

cell mediated not Ab mediated

Question 8

Type IV. how does it work

Answer 8

T cell mediated H or delayed H (TYPE IV)
-macrophage presents Ag to T cell–T cell is sensitized–cytotoxic T cells–T cells destroy Ag bearing cells–inflammation and damage

Question 9

2 types of T cell mediated H or delayed H

Answer 9

-1-direct (stat)
((even if a virus has no cytotoxic effects eg hepatitis it will still kill))
-2-Delayed (days) needs time to produce lymphokines eg TB test where we waited 2 days until the reaction
eg contact dermatitis with poison ivy which takes 2 days to appear?

Question 10

How are T cell mediated H and Delayed H different

Answer 10

fig 19-6
Primed CD4 cells (TH) activate CD8 (TC) cells which target cells by direct toxicity and activate CD4 (TH) which releases cytokines.
Cytokines are what produce the delayed H response whereas the TC cell produces the direct cell mediated cytotoxicity

Question 11

how does autoimmunity occur?

what results from this?

Answer 11

self Ags are normally tolerated but when this tolerance is lost the self is considered foreign

• Abs will target self Ags
• Ab+Ag–inflm, damage and necrosis

Question 12

how can self tolerance be lost? and you end up with autoimmunity

Answer 12

1=abnormal T cell acitivity
2=molecular mimicry
3=expoure of previously masked self Ag

Question 13

autoimmunity: if you have abnormal T cell activity what could occur

Answer 13

eg no T cell suppression they can run wild and cause damage

most likely when not enough its immunodeficiency?

Question 14

autoimmunity: what does molecular mimicry entail?

Answer 14

when there is similarity in the epitope there is a mistaken identity
-similarity in one area of the protein molecule (the epitope) results in confusion and destruction despite it being self

Question 15

autoimmunity: how is a previously masked self-ag exposed that previously wasnt. describe this process

Answer 15

eg by disease such as SLE (systemic lupus erythematosis. Ags targeted are the nuclei and therefore almost all cells of the body

-during embryogenesis the exposed Ags are gradually incorporated into the tissues and structures and no longer exposed. Because the immune system isnt dev. yet it wont recog the self Ags when theyre exposed by disease and therefore it will destroy them