Antibodies and gene rearrangement

Question 1

Describe Adaptive immunity

Answer 1

has memory- second response is stronger and more rapid than the primary response

affinity of B cells towards antigen increases with time and persistence of antigen.

a individual is born with a range of B and T lymphocytes

Question 2

Adaptive immunity origins

Answer 2

relies on gene rearrangement of recombination

Transposase are called RAG1 and RAG2 (Recombination activation Genes)

Question 3

Lymphocytes involvement with adaptive immunity

Answer 3

lymphocyte represent a different antigen specificity randomly produced by rearrangement of the genes coding for the antigen receptors

Question 4

Describe immunoglobulin (Ig) protein fold

Answer 4

IG protein domain is called a B barrel

It is two repeating units

two anti parallel B plated sheets joined in the middle by a disulphide bond

Question 5

Antibody protein structure

Answer 5

consists of 4 protein chains

linked by a disulphied bond

Y shaped withn 2 flexible arms with antigen binding sites

FC region is the effector region

2 light domains in Light chains and 4 domains in Heavy H chain

1H chain is linked to 1L chain

Question 6

describe the H chain link

Answer 6

they have a disulphide link

Question 7

State the 5 Ig classes

used GAMED

Answer 7

IgM
IgG
IgD
IgE
IgA

Question 8

What is IgM

Answer 8

default naive B cell
forms the b cell

antigen receptor

10 antigen binding sites

reacts strongly to surfaces such as microbes

good at fixing complement with 5 Fc regions that can bind to C1

Question 9

what is affinity

Answer 9

sum of the attractive molecular forces at two surfaces exceeds the repulsive force

higher the affinity the fewer molecules it takes per unit column to associate and to dissociate

Question 10

what is avidity

Answer 10

results from multiple affinity contacts. Strength of binding can be orders of magnitude

higher than the individuals affinities

Question 11

what is complementarity

Answer 11

antibody can form complementarity to virtually anything because the potential amino acid diversity at the antigen binding sit is vast

Question 12

what is IgG and IgE

Answer 12

serum

Question 13

what is IgD

Answer 13

serum & membrane

Question 14

what is IgA

Answer 14

serum + mucosa

Question 15

describe the antigen binding site

Answer 15

3 regions called complemetarity Determining Regions (CDR)

3 loops that connect the strand in the 1st domains of the H and L chains

There are 2 identical anitgen binding sites

Question 16

Describe the Germ- line Ig locus and recombination

Answer 16

arranged into clusters called 
Variable, 
Diversity, 
Joining and 
Constant regions

Light chains have no D segement

Question 17

Describe the Recombination activation gene in the Ig locus

Answer 17

RAG1 and RAG2

are responsible for rearrangement and are only active in B and T lymphocytes

Question 18

Describe recombination in the H gene locus

Answer 18

V / D/ J/ C

D to J then V goes to the D

Question 19

Describe recombination in the L gene locus

Answer 19

v to the J

as light chains have no D segment

Question 20

Describe clonal selection and immune repertoire

Answer 20

It randomly makes as many receptor combinations as possible and then allows the pathogen to select those clones that are useful

one B cell= one antigen specificity

Question 21

describe the affinity maturation in B cells

Answer 21

massive amount of B cells generates before birth with a unique B cell receptor

Random somatic hypermutation of Ig gene results in some clones with a higher antigen receptor affinity

mature B cells become plasma cells secreting soluble Ig

B cells reside in lymph nodes as long term memory cells

Question 22

What is the fundamental mechanism maturation in B cells

Answer 22

FUNDAMENTAL MECHANISM BEHIND APATIVE IMMunity, memory and immunisation

Affinity maturantion is the reason why immunization works.