Chapter 5: Antibody Structure & Effector Function

Question 1

Surface Ig

Answer 1

Embedded in B call membrane. Acts as BCR
Can transducer activation signals upon antigen binding
Each cell expresses multiple copies

Question 2

Secreted Ig

Answer 2

Secreted by B cells (lacks extra c domain present in surface Ig)

Question 3

Immunoglobulin structure (describe)

Answer 3

Two chains-heavy and light
Chains held together by disqualified binds
Chains have variable and constant regions
V=antigen binding
C= effector function

Question 4

CDR

Answer 4

Complemantarity Determining Regions or hypervariable regions
3 on each variable region
Contains most of the variability, mostly in CDR3 (due to vj/vdj joining)
CDR1 and 2 Germline encoded, not 3 because it is due to joining/rearrangement

Question 5

Types of light chains (Ig)

Answer 5

Kappa and lamba.

Same type of light chain is found on both arms

Question 6

Types of heavy chains (Ig)

Answer 6

Type determines isotope/effector function

5 types

Question 7

IgG

Answer 7

Monomer (bivalent)
Major class in secondary response
Large hinge region (flexible arms)
High affinity

Question 8

IgM

Answer 8

Has extra C domain (surface Ig)
Pentamer
High avidity and low affinity
Oligomerization by J chain

Question 9

IgA

Answer 9

Dimer (tetravalent)
Major Ig secreted in GI and respiratory tracts
Oligomerization by J chain
Uses secretory component for trancytosis into luminal space

Question 10

IgD

Answer 10

Low abundance

Mainly cell associated

Question 11

IgE

Answer 11

Involved in allergic reactions
Involved in response to parasites
Binds to mast cells and induced degranulation
Has extra C domain

Question 12

Affinity

Answer 12

The strength of binding of one molecule to another at a single site

Question 13

Avidity

Answer 13

Sum total of the strength of binding between two molecules or cells to one another (where multiple binding sites are involved)

Question 14

Antibody effector functions: direct

Answer 14

Involves antigen recognition of Fab part of Ig

Question 15

Antibody effector functions: indirect

Answer 15

“Targeting mechanism”

Involves Fc part of Ig

Question 16

FcR

Answer 16

Fc receptors
Can bind to Fc region of an antibody
FcGamma most common

Question 17

ADCC

Answer 17

Antibody dependent cell mediated cytotoxicity
When antibody binds to target cell via variable region and binds to an NK cell (using FcR) cross linking triggers NK killing

Question 18

Degranulation

Answer 18

IgE binds to parasite/allergen, IgE binds FcEpsilonReceptor in mast cell and cross linking triggers degranulation

Question 19

Complement activation

Answer 19

Ig binding to C1Q via Fc initiates classical pathway
Only by IgG and IgM
Free antibody does not activate C1Q