Immunology Lecture 4_Antibodies

Question 1

Define Immunoglobulin (antibody)

Answer 1

Immunoglobulins (IgX) are protiens that are secreted by B cell lymphocytes to neutralize pathogens. They do this by by binding to a pathogen or it’s products and recruting other leukocytes to destroy the pathogen.

Question 2

Identify the following structures on an IgX: Heavy chains, light chains, constant region, veriable region, flexible hinge (what tertiary bond forms this), antigen binding site, C terminus and N terminus, Fc, and Fab

Answer 2

Draw a picture, refer to slide 5 if needed

Question 3

What does the Fab region do?

Answer 3

Fragment Antigen Binding (Fab) is the part of the IGX that binds to the epitope on the antigen (they are epitope specific)

Question 4

What does the Fc region do?

Answer 4

Fc binds to Fc receptors on other cells, often to iniciate phagocytosis

Question 5

Define Autoantigen

Answer 5

A self molecue that incorrectly induces an immune response

Question 6

Explain combinatorial diversity

Answer 6

recombination activating gene (RAG) mediates multiple V -(D)-J combinations in the veriable protion of the heavy and light chains.

Question 7

Define Junctional diversity

Answer 7

Additions and deletions of necleotides at junctions durring recombination.

Question 8

Define valence

Answer 8

Valence is the number of pathogen binding sites. A single anti body has a valence of 2

Question 9

Define Affinity

Answer 9

The strength of binding at a single site

Question 10

Define Avidity

Answer 10

Total strength when all binding sites are included (Avidity increases as valence increases similar to the strength of a rope as you add strands)

Question 11

What kind of IgX do naive B cells have as BCR

Answer 11

both IgM and IgD

Question 12

What kind of IgX do memory b cells express as BCRs

Answer 12

they can express any one isotype as a BCR

Question 13

Where is the IgG isotype high?

Answer 13

in blood and epithelial tissue

Question 14

Where is the IgA isotype high?

Answer 14

at the mucosal surfaces

Question 15

How is the Classical Complement Cascade triggered?

Answer 15

It is triggered with one Pentameter of IgM or at least 2 monomers of IgG

Question 16

Describe Opsonization. What IgX typically triggers it

Answer 16

Antibodies bind bind to a pathogen and then Fc receptors on phagoctotic cells bind to the Fc end of the antibody and begin phagocytosis. This is typically meadiated by IgG

Question 17

Describe Antibody dependent cellular cytotoxicity (ADCC). What IgX meadiates it

Answer 17

Viral infected cells express antigenic protiens on their surface. Antibodies bind to these cells then bind to NK cells via Fc receptors. NK cells are triggered to kill the infected cell. This is typically mediated by IgG

Question 18

How do IgXs interact with mast cells. What IgX is envolved

Answer 18

IgEs bind to mast cells via Fc receptors. when the IgE binds to an antigen, it trigers a massive release of hisamine from the mast cell.

Question 19

How do IgXs interact with eosinophils? What IgX is envolved?

Answer 19

IgEs opsonize a parasite. Then eosinophiles bind to the IgE coated parisite via Fc receptors and are triggered to degranulate.

Question 20

How does IgM exist in the body as both a BCR and secreated protein?

Answer 20

exists as a monomer in the BCR form and a pentamer in the secreted form

Question 21

What is the first antibody formed during a primary response?

Answer 21

IgM

Question 22

Describe Hyper IgM

Answer 22

It is a rare disorder where a person has elevated levels of IgMs. This leads to increased decreased rates of other isotypes which leads to dificult to treat infections

Question 23

What is the function of IgD

Answer 23

The function of IgD is unclear. It has very low serum consentrations. Higher rates of IgD producing plasma cells are found in the respiratory tract as compared to the digestive tract

Question 24

Describe neutralization

Answer 24

it is when secreted antibodies bind an antigen and prevent it from passing through its target barrier. IgA prevents antigens from crossing epithelial barriers and IgG prevents antigens from entering target cells

Question 25

List the 4 functions of IgG and what part of the immune respons it participates in

Answer 25

the four functions are Nutralization, opsonization, complement activation (of the classical pathway) and ADCC. It is the predominante isotype in the late primary and memory response

Question 26

Where does IgA exist as a dimer/monomer? How abundent in blood, where else is it found.

Answer 26

IgA exists as a monomer in blood and a dimer in secretions. It composes 10-15% of serum IgXs and is the predominant IgX in secretions including saliva, tears, and breast milk.

Question 27

What is a likely out come of antibody deficiencies?

Answer 27

recurrent pyogenic infections and difficulty with encapsulated bacteria