Antibody biology

Question 1

which response do B cells activate

Answer 1

humoral response, responsible for producing antibodies.

Question 2

where do b cells originate and mature

Answer 2

bone marrow

Question 3

what happens to the B cells upon activation with antigens

Answer 3

they differentiate into plasma cells which are antibody-producing factories

Question 4

what do plasma cells secrete

Answer 4

antibody of the same specificity as the membrane-bound immunoglobulin expressed by their B cell precursor

Question 5

FAB

Answer 5

fragment antigen binding - responsible for binding antigen

Question 6

FC

Answer 6

fragment crystallisable - responsible for effector function

Question 7

what does the flexible hinge of IgG allow

Answer 7

allows for both arms to bind to many arrangements of antigens on pathogen surfaces

Question 8

what are the two types of light chains

Answer 8

Lambda and Kappa

Question 9

In any individual antibody molecule, are the chains the same or different

Answer 9

both light chains

Question 10

which chain determines the class of antibodies

Answer 10

heavy chain

Question 11

what do antibodies fold into

Answer 11

globular domains with distinctive 3d structure

Question 12

what do the globular domains comprise of

Answer 12

2 beta sheets with a total of 7 or 8 antiparallel beta strands which are linked by disulphide bridge to form a beta parallel.
this folded structure is known as the “immunoglobulin fold”

Question 13

what do hypervariable loops form

Answer 13

antigen binding site

Question 14

what are hypervariable loops known as

Answer 14

complementarity-determining regions (CDRs)

Question 15

what happens when VH (variable heavy) and VL (variable light) domains are paired

Answer 15

their 6 CDRs creae the antigen-binding site

Question 16

what is an epitope

Answer 16

An epitope, also known as an antigenic determinant, is the specific region on an antigen that is recognized and bound by an antibody, a B cell receptor, or a T cell receptor.

Question 17

what is a linear epitope

Answer 17

epitopes in protein antigens may comprise a single stretch of polypeptide chain

Question 18

what is a discontinuous epitope

Answer 18

3D folded like structure where the polypeptide chain is not continuous

Question 19

what can epitopes bind to

Answer 19

pockets, grooves, extended surfaces or projections in antigen binding sites

Question 20

each individual has an antibody repertoire (available antigen specificities) of approximately how many

Answer 20

1011

Question 20

epitopes for antibodies are exposed where

Answer 20

on pathogen surfaces

Question 21

how is the antibody repertoire achieved

Answer 21

Ig genes are organised differently to other genes, in all cells except B cells, Ig genes are in fragmented form that cannot be expressed
Ig heavy and light chain loci consist of families of gene segments, arrayed sequentially along the chromosome
* They are inherited in this form through egg and sperm (germline)Therefore their arrangement is termed “germline configuration”
* In developing B cells, Ig gene segments must be rearranged to assemble functional light and heavy chain gene

Question 22

VH domain is encoded by what

Answer 22

V (encodes most of the V domain) ,D (diversity segment) and J (Joining segment) gene segments

Question 23

VL domain is encoded by what

Answer 23

V (encodes most of the V domain) and J (Joining segment) gene segments

Question 24

at which point in B cell development does Ig gene rearrange in the H chain

Answer 24

early pro-b cell: D-J rearranging
late pro - b cell: V-DJ rearranging

Question 25

at which point in B cell development does Ig gene rearrange in the L chain

Answer 25

small pre b cell: V-J rearranging

Question 26

when is the DNA spliced out

Answer 26

during early development of the B cell

Question 27

what is the D gene segment joined to and what is the DJ segment joined to

Answer 27

D is joined to J and V is joined to DJ

Question 28

what is recombination coded by

Answer 28

recombination signal sequences
12 and 23 base pair sequences

Question 29

what is the 12/23 rule

Answer 29

genes with the 12 base pairs can recombine with 1 with the 23 base pair spacer

Question 30

what is the mediator to organise the splicing

Answer 30

VDJ recombinase

Question 31

what is the VDJ recombinase made of

Answer 31

RAG (recombination activating gene) 1 and RAG2 RAG-1 and RAG-2 proteins work together to initiate the recombination process by recognizing specific recombination signal sequences (RSS) flanking the variable (V), diversity (D), and joining (J) gene segments.

Question 32

how does the RAG complex work

Answer 32

The RAGS bind to the 12 and 23 base pairs on the V and J RSS. The RAG complexes then come together and align the RSSs and cleaves the DNA at ends of gene segments.
That forms a DNA hairpin and a clean break at the heptemer ends. The RAG complexes hold the DNA in place while broken ends rejoined by DNA repair enzymes = nonhomologous end-joining. Coding joint formed in chromosome, signal joint removed piece of circular DNA.

Question 33

what creates the palindromic nucleotides

Answer 33

a nick that opens the hairpins can occur at several different positions

Question 34

diversity of Ig repertoire generated by main processes
Combinatorial diversity

Answer 34

many of the copies of each gene segment type which can combine in many different ways

Question 35

diversity of Ig repertoire generated by main processes
Junctional diversity

Answer 35

nucleotides added or subtracted at joints between gene segments during enzymatic steps

Question 36

diversity of Ig repertoire generated by main processes
combinations of light chain heavy chain

Answer 36

many different combinations of light and heavy chains v regions that pair to form antigen binding site

Question 37

diversity of Ig repertoire generated by main processes
somatic hypermutation

Answer 37

somatic hypermutation introduces point mutations into rearranged V region genes of activated B cells

Question 38

in the CH gene what do the exons code for

Answer 38

individual Ig domain

Question 39

s