Immuno

Question 1

Describe the pathophys of adenosine deaminase deficiency → SCID

Answer 1

AR condition → mutation of adenosine deaminase needed to convert adenosine → inosine → adenosine accumulates in cells → cytotoxic to B and T cells → cellular and humoral deficiency

Question 2

How do eosinophils work?

Answer 2

they damage helminth larvae via an antibody-dependent (IgE) cellular toxicity mechanism which may involve major basic protein

Question 3

What immune deficiency leads to chronic giardiasis?

Answer 3

IgA deficiency (e.g. X-linked agammaglobulinemia and common variable immune deficiency)

Question 4

Describe the immune response to TB

Answer 4

Mø infected w/ TB produces IL 12 → stimulates T cells and NK cells to produce IFN-gamma → phagocyte IFN-gamma receptor dimerization → janus kinase 1 & 2 → STAT1 nuclear signaling and IFN-gamma-related gene transcription → enhanced bacterial killing

Question 5

What will patients with an autosomal recessive deficiency in IFN-gamma receptor require?

Answer 5

lifelong treatment with antimycobacterial antibiotics (note that they can get BCG infection if they get the vaccine)

Question 6

What does C3 deficiency predispose to?

Answer 6

recurrent infection by encapsulated organisms

Question 7

What does C5-9 (membrane attack complex) deficiency lead to?

Answer 7

recurrent infection by N. meningitidis or N. gonorrhea

Question 8

Describe isotype switching

Answer 8

helper T cells activate naive B cells through two mechanisms:

1. CD40 ligand on T cell → CD40 receptor on naive B cell
2. Cytokines: IL-4 → IgE class switching; IL-5 → IgA class switching

Question 9

What causes leukocyte adhesion deficiency? What are the symptoms?

Answer 9

defect in CD18 (a component in many integrins) → leukocytes can't adhere or transmigrate through endothelial walls
Symptoms: 
1. delayed separation of umbilical cord
2. recurrent infections w/out pus
3. poor wound healing

Question 10

How do acidification of lysosomes and antigen presentation relate?

Answer 10

antigens are loaded onto MHC II receptors in APCs in acidified lysosomes; without acidification, APCs would not interact with T cells

Question 11

Give some examples of infections that indicate humoral immunodeficiency and some that indicate T-cell deficiency

Answer 11

Humoral:
bugs causing otitis media (H. flu, S. pyogenes, Moraxella)
T-cell:
PCP, mucucutaneous candidiasis