Chapter 4 sections 7-16 Flashcards
chapter 4 parts 2 and 3
flow cytometry
use of fluorescent labeled monoclonal antibodies to ID cells
Immunoglobulin diversity before B cells encounter Antigen
Germline configuration of gene segments encoding for Igs are inherited via egg and sperm
and encoded in gene segments on regions of chromosome 22,2,14
but only expressed in B cells following successful gene rearrangement
Occurs on chromosome 22,2 14
gene segments that code for Ig diversity that was inharerited via egg and sperm
Light chain formation via somatic recombination
2 options for Light chain gene formation
from the germline DNA lamda variable segments is selected
which is joined to
J segment and one of the constant segments
or
from the germline DNA kappa variable segments is joined to j segments and a constant kappa segment
Heavy chain formation via somatic recombination
2 options for Heavy chain gene formation
from the germline DNA 1 H variable segments is selected
1D segments
which is joined to 1J segments
and one of the Mu constant segments + the gene for the transmembrane component finally V and DJ segments are join
all the components of heavy chain gene
1 H variable segment +((1D segment+1J segment)+one Mu constant segment + transmembrane component)
all the components of light chain gene
1 lambda variable segment + 1 j segment + 1 constant segment
or
1 Kappa variable segment + 1 J segment + 1 constant Kappa segment
mu version of H chain results in
IgM production
somatic recombination
the process of choosing of one of many gene segments to form an exon that can be transcribed
how to find # possibility of type of chain kappa light chain lambda light chain heavy chain these are only present in B cells
(# of possibilities for Variable region) X (#of possibilities of J segments)
how many variations of diversity result from somatic recombination and combinatorial association
1,628,400 posiblities in the variable region alone aka tons of diversity
this impacts the hypervariable regions 1& 2
combinatorial association
when light and heavy chain bind together their impact on antigen binding
HV
hyper variablility
Recombination signal sequences (RSS)
directs somatic recombination, RSS that flanks the V and D and J segments there are 2 types
these provide a point for enzymes to cut and rejoin the gene segments
2 Types of RSS
hepatamer
and nonamer
these are separated by a 12 base pair segment or a 23 base pair segment
length of bp segment that separated the 2 types of RSS
12 or 23 bp length segments
V(D)J recominase
enzyme that clips out RSS segment and rejoins gene segments
this enzyme is only made in lymphocytes
enzymes associate with RAG1-2 gene to for RAG complex that forms DNA into a hairpin and then cleaves and rejoins it bringing V and j segments together
RAG-1 and 2
recombination -activating genes, these gene products and other enzymes associate to for RAG complex that forms DNA into a hairpin and then cleaves and rejoins it bringing V and j segments together
Junctional diversity
occurs when enzymes of RAG complex join the gene segments VD and J
palindromic nucleotides (P nucleotides)
nucleotides that are read the same forward and backward the RAG complex adds these P nucleotides by nicking one strand of DNA at the terminus
at Junction
enzyme can remove gremlin encoded nucleotides or TdT enzyme can add nucleotides that are not encoded in the Germline
N nucleotides
nucleotides that are not encoded in gemline
RAG forms
the hairpins and ceaved one strand of DNA
TdT
terminal deoxynucleotidyl transferase,
acts as addition of N nucleotides which were never germline