Antibody production Flashcards
heavy chain immunoglobulin domains
4, 1 variable and 3 constant held together by disulfide bonds
light chain immunoglobulin domains
2, 1 variable and 1 constant held together by disulfide bonds
3 hypervariable regions
CDR1, 2, and 3 all involved in binding the antigen
membrane associated antibodies
include the membrane and cytosol exons in the antibody transcript
secreted antibody form
uses a poly a cleavage site to rid of the membrane and cytoplams exons from the antibody transcript
T cell receptor makeup
has alpha and beta chain or has gamma and delta chain,
has CDR regions and also has constant and variable regions on each chain
5 mechanisms for antibody diversity
many Vh and Vl genes
combinatorial association of different V, D, and J gene segments
junctional diversity by nucleotide addition
combinatorial association of Vh and Vl
somatic hypermutation…non genome encoded
heavy chain gene regions
V, D, J, and C
VDJ all in Vh region
light chain gene regions
V, J, and C
CDR locations in heavy chain
1,2 in V region
3 in D and J regions
CDR locations in light chain
1,2 in V region
3 in J region
two light chain genes
kappa and lambda
both have a lot of options for V region
kappa has 5 options for J region
lambda has four options for J and C regions
VDJ recombination process
chromatin opened up and allows for genes to be brought close together and a double stranded nick to be made, the variable VDJ options are now able to be transcribed and spliced to become a functional mRNA
sometimes nucleotides can be added or removed when nick is made, so leads to more variation
heavy chain genes
only one gene, has many options for V, many for D and a few for J
Recombination signal sequences
mediate recombination
7 nt stretch followed by 12 or 23 base pair followed by 9 nt AT rich stretch
must have 12 and 23 recombinating together, never 12 and 12 or 23 and 23
RAG 2 and RAG 1 roles in VDJ recombination
RAG 2 recognizes methylation going on, it calls for RAG 1 to come in and cut/join the V/J segments
P nucleotide addition in VDJ variability
at hairpin turn, artemis protein cuts strands and relocates to other strand then repair adds nucelotides for matching, when the V and J come together nuclease removes mismatches and polymerase repairs and ligase links
N nucleotide addition in VDJ variability
just adds nucleotides onto the end of the strands, can be any of the four nucelotides
CDR3 diversity
most diverse CDR because it is in D and J region in heavy chain and in V and J region in light chain
while 1 and 2 are only in V region in light and heavy
allelic exclusion in antibody variation
if one allele leads to good antibody then other stays repressed, but if it leads to bad antibody then other allele gets expressed
light chain isotype exclusion in antibody variation
kappa is first and if successful then dont do delta
but if kappa is bad then do delta
so you see kappa in about a ratio of 2:1
class switching of antibodies
activated by CD40 and leads to a different C region being transcribed by recombining to different region of gene and cutting out the genetic material between sites
affinity maturation in V regions
really high mutation rate (1000X normal), mutations in V region make the antibody have better affinity for antigens, lower Kd
T cell receptor diversity
has different options for V,D and J regions like antibodies, have variable CDR1-3 regions, CDR3 is most variable, have VDJ joining techniques and P/N diversity like antibodies
DO NOT HAVE SOMATIC MUTATIONS
Severe combined immunodeficiency
mutations in recombination enzymes like RAG 1 and 2, artemis enzymes result in loss of B and T cells
GENE THERAPY
Hyper IgM syndrome
genetic defects in AID or UNG lead to inability of class switching or somatic mutation
no class switching so all IgMs and not able to fight infection
AID
protein involved in class switching and somatic mutation by deaminating Cs and making Us
UNGs
protein involved in class switching and somatic mutation that can remove the Uracil and leads to mutation or nicks in DNA
Lymphoid tumors and class switching
oncogenes like MYC can often be close to where AID will cause switch in the antibody and can get placed within the switch and is therefor over expressed and can lead to B and T cell tumors
