Humoral Immunity Part 2

Question 1

How long does a primary immune response take?

Answer 1

7-10 days

Question 2

Describe the secondary immune response.

Answer 2

Takes 3-5 days to peak. Stronger and faster than primary immune response

Question 3

Compare cell activation in primary vs secondary immune response.

Answer 3

Primary response activates on naive b cells. Secondary activates both memory and naive b cells.

Question 4

How is the humoral immunity controlled?

Answer 4

Immune complexes binds to b cell at Fcy receptor on CM. This leads to cross-linking of membrane bound Ig and FcyR and removes the phosphate from ITM (signaling membrane protein).

Question 5

What can antibodies do?

Answer 5

Opsonize, neutralize, Antibody-dependent cellular cytotoxicity. Activate complement

Question 6

Describe status of membrane bound antibodies vs secreted ones.

Answer 6

All membrane-bound antibodies are monomers. When secreted they become polymers. They polymerize when a J chain joins.

1. IgA can form mono/di/trimers
2. IgM forms a pentamer.
3. Secreted IgG and IgE remain monomers
4. IgD is never secreted.

Question 7

What is IgAs main function?

Answer 7

Mucosal immunity; Found in mucus, tears and milk

Question 8

What is IgDs main function?

Answer 8

Activates naive B cells

Question 9

What is IgEs main function?

Answer 9

Mast cell activation; Defends against worms

Question 10

What is IgGs main function?

Answer 10

Opsonization, C’ activation, etc

Question 11

What is IgMs main function?

Answer 11

Activates naive B cells, C’ activation.

Question 12

What can all antibodies do?

Answer 12

Neutralize

Question 13

Which cells can bind IgG?

Answer 13

Professional APCs, Eosinophils, Nk cells, and B cells all have FcyR.

Question 14

Which cells can bind IgE?

Answer 14

Eosinophils, Mast cells, and Basophils all have FceR

Question 15

Discuss Antibody-Dependent Cellular Cytotoxicity.

Answer 15

CD16 on Nk cells binds to the Fc region of IgG. Cross linking activates the NK cell to induce exocytosis of granules.

Question 16

What does the basal side of epithelial cells in the GI, respiratory tracts, tear ducts and mammary glands have?

Answer 16

They all have poly Ig receptor; Binds to the J chain and activates transcytosis. On the apical side, an enzyme cleaves the poly Ig receptor releasing the secretory component. This increases the half-life of IgA and IgM.

Question 17

Why does IgG have the longest half-life in serum?

Answer 17

FcRn can be found on placenta, endothelial cells and phagocytic cells. Recycles the antibody.

Question 18

Discuss passive immunity

Answer 18

Fetal endothelial cells express FcRn on the basal side, exposed to maternal blood in the placenta. The FcRn-maternal IgG is transcytosed across into fetal blood vessels.