Autoimmunity 3

Question 1

How are Type II hypersensitivity complement and Fc mediated inflammation carried out?

Answer 1

antibody complexes are deposited in extracellular tissues/matrix

Question 2

Once antibodies are deposited in tissue, during type III rxn, what are the insuing events?

Answer 2

IgG or IgM activate complement which recruits inflammatory cells, causing local tissue damage

Question 3

Describe the disease mechanism in Goodpasture Syndrome.

Answer 3

body produces antibodies agains the basement membrane, particularly apparent in the lung and the kidney

Question 4

How are Type II hypersensitivity antibody mediated cellular dysfunction inflammation carried out?

Answer 4

antibodies are directed against cell surface receptors, which dysregulates cellualr funciton without inflamtion or direct cellular injury (i.e. Graves disease/TSH-R or Myasthenia gravis (Ach-R)

Question 5

How is type III hypersensitivitity mediated?

Answer 5

antigen combines ith anibody in circulation and the resulting immune complex can be deposited in b.v. or tissue, they can also activate complex when deposited

Question 6

Desposition of immune complex in type II reactions results in what events?

Answer 6

antibody complezes activate complex which induces local inflammation; additionally, inflammatory cells may be further activated through Fc-R and platlets may aggregate due to Hagemean factor activaiton (Factor XII)

Question 7

What is fibrinoid necrosis?

Answer 7

acute necorizing vasculitis, immune complex causes lots of inflammation and down stream ischemia

Question 8

Name 4 diseases caused by immune complex disease and their associated antigen.

Answer 8

SLE (DNA/nucleoproteins); Post strep GN (strep cell wall) Polyarteritis Nodosa (hepatitis surface antigen) and reactive arthritis (yersinia bacterial antigen)

Question 9

How is type IV hypersensitivity mediated?

Answer 9

initiated by antigen activated (sensitized) T cells – immune response against intracellular pathogens

Question 10

What are the two types of cell mediated (Type IV) hypersensitivity.

Answer 10

delayed type hypersensitivity (CD4+) and cell mediated cytotoxicity (CD8+)

Question 11

What cell types cause the inflammation of type IV hypersensitivity.

Answer 11

CD4+ cells, both TH1(macrophages) and TH17(neutrophils) cells

Question 12

How to APC induce macrophage or neutrophil recruitment?

Answer 12

APC produce IL-2 (TH1- INF-gamma) to activate macrophages and IL-23 (TH17-IL-17 for neutrophil recruitment

Question 13

Give an example of a delayed type hypersentivity reaction.

Answer 13

tuberculin skin test causes a reaction by CD4+ t-cell if patient was previously exposed to TB

Question 14

Describe the first exposure that is require dfor a delayed type hypersensitivity.

Answer 14

APC present antigen to CD4+ cell and secretes IL-12 causing differentiation of TH1 cells, some of which circulate dna wait for antigen re-exposure

Question 15

Describe re-exposure in delayed type hypersensitivity.

Answer 15

activated TH1 memory cells secrete INF-gamma qhich activates macrophages (the key mediator of DTH)

Question 16

What is the action of INF-gamma on macrophages?

Answer 16

activates macrophages, increases phagocytosis of microbes, increases class II expression for increased antigen presentation and induces secretion of IL-12 for TH1 feedback activation

Question 17

In chronic/presistent antigen delayed type hypersensitivity, how is the immune response modified?

Answer 17

granuloma formation occurs, macrophages transform into epithelioid histiocytes and may fuse to form a multinucleated giant cell (which is further surrounded by lymphocytes

Question 18

Describe the mediators/mechanism of cell mediated cytotoxicity.

Answer 18

perforins (perforate cell membrane- osmostic lysis) and granzymes (enter perforations and activate caspases) are released on contact with target cell