Immunology 3

Question 1

Recognition Specificity vs Effector Specificity

Answer 1

Recognition: Determines which antigens are recognized. Mediated by Fab region on antibodies.
Effector: Determines which defines mechanisms are invoked. Mediated by Fc region on antibodies

Question 2

6 Antibody effector Mechanisms

Answer 2

1. B Cell Receptor: Antigen eaten then processed and then put on surface to be recognized by T-helper cell.
2. Simple Binding: Blocking active site to prevent virus/bacteria from entering cell
3. Cell-surface binding via Fc region: Antibody binds to Fc region on cell which then binds Antigen!
4. Opsonization: Antibodies coat bacteria, with Fc region sticking out from bacterial surface, then binds to Fc receptors on activated macrophages, stabilizing interaction!, uses “velcro”. Antibodies helps the bacteria not be so slimy/slippery!
5. NK cell ADCC and mast cell degranulation: Nk cell can’t get antigen out of solution… not high enough Fc affinity! Thus can kill IgG coated cell!
6. Complement Activation:

Question 3

Mast Cells Fc Affinity

Answer 3

Mast cells have highest affinity Fc receptor! They bind IgE! All mast cells in body are covered in IgE! Thus concentration of IgE in serum is very low! If high… person has an allergy! Mast cells have a job to dump out histamine!

Question 4

Complement

Answer 4

Set of circulating serum proteins that are activated in a sequential proteolytic cascade. Two different ways for activation, classical pathway, and alternate pathway.

Question 5

Classical Pathway Activation of Complement

Answer 5

Initiated by antibody/antigen complexes. Use IgG or IgM… keeps assembling bigger complexes!

Question 6

Alternate Pathway Activation of Complement

Answer 6

Opsonization:Complement is a proximity bomb… it spontaneously forms complexes which attach to all cells in our body. It has blue tags which spray on the humans and cat. Also releases a stink. The human cells can use tissue and wipe off the blue tags, but the cat (bacteria) can’t, and it amplifies! The Sheriff comes because of the smell! It sees who has the blue tags on it and takes the cat away. The cat is a neutrophil and destroys these cats.
Also Membrane Attack Complex (MAC): Once complement coats all these cells, our cells can wipe it off, sometimes tags will dig holes in bacteria and then allow fluid to rush in due to osmotic gradient and thus burst cell! Most cells not susceptible to MAC.. thick walls!

Question 7

Four things that can happen when complement gets activated

Answer 7

1. Cell lysis - hole in cell wall
2. Phagocytosis - binding of opsonized bacteria to complement receptors on macrophages
3. Mast cell Activation and Neutrophil recruitment
4. Solubilization of immune complex

Question 8

What needs to happen to activate complement?

Answer 8

• Must bind to two or more Fc portions to activate complement
• Can bind to IgM on antigens

Question 9

Opsonization

Answer 9

Since antigens are usually slippery, Macrophages can’t catch them out of solution! So Antibodies bind to antigen, and then allow macrophages with Fc to bind to the Fc region on the antibody creating complexes which macrophages can then bind to in a velcro-ish effect! This then makes phagocytosing them easier.

Question 10

IgM

Answer 10

Good at activating complement!

Question 11

ADCC

Answer 11

IgG coats target cell or antigen. This coating then allows NK cells to have an increased affinity which allows them to bind to and kill the target cell.