B cell antibodies, TCR

Lymphoid stem--->pro-B--->pre-B--->immature B cell--->mature B cell--->activated B cell--->memory B cell--->plasma cell

Lymphoid stem cell--->Mature B cell

Activated B cell--->Plasma cell

in pre-B cell stage, only mu H chain is expressed

• 1. L chains are made and interact with H chains
• 2. tolerance induction

the B cell is able to express IgM AND IgD on its surface; monospecific

by specific antigen; can now proliferate and secrete IgM; class switching can now happen (un altre' classe possono mostrare adesso)

bc always secreting antibodies at high rates (presence of polyribosomes and vesicles and active golgi as well)

4: V, D, J, C

3: V, J, C

• 1. D to J
• 2. V to DJ
• 3. VDJC

*H chain expressed before L chain (pre-B)

• 1. V to J
• 2. VJC

recombination signal seq: highly conserved 7bp and 9bp seq that are directly adj to each Ig gene segment (V, D, J)

recog by RAG prot

the seq btw the RSSs flanking the VDJ regions must be of diff lengths; only 12/23 pairings

spacer seq are NOT conserved whereas RSSs are conserved

P and N nuc additions results in imprecise joining of ends and presence of variation (see notes for mech)

reading frame shift: leads to a non func antibody prot; called non-productive rearrangements

cleaves chains to result in hairpins at the end of each DNA strand at coding ends

opens hairpins in junctional diversity, making a palindromic seq

N nuc additions to palindromic ends created by artemis-DNA-Pk

expression of a gene from only one of two chromosomes encoding that gene; occurs for H and L chains

H chain is first one to be rearranged (V-DJ only bc D-J does not participate in rearrangement); if first strand not successful, then attempts at second strand; if second strand not successful then cell dies.

K-L chains rearrange before L-L chains are given a chance to rearrange; L-L chains only given a chance if K-L chains fail to rearrange at both strands

• -contains phobic TM tail and cytoplasmic tail at carboxyl end
• -each receptor assoc w/ two Ig-a an Ig-B heterodimers (have TM and cytoplasmic tails for signaling into B cell)

genes for TM and cytoplasmic tails are on genes for both secreted and membrane form of Ig; diff is which cleavage and polyadenylation sites are recog

mu and delta genes are both on B cell genome; diff is during processing of pre-mRNA

IgD present on mature B cells (low amts on immature) in higher amts than IgD on mature cells

• acidic a chain dimer
• basic B chain dimer
• glycoproteins
• TM region
• cytoplasmic tail
• V and C regions w/in each a and B chain

gamma/delta TCR; not MHC restricted; can recog antigens w/ non-classical MHC molecules

TM extracellular gamma, delta, epsilon (x2): CD3 complex (ALWAYS PRESENT..needed to transmit signal to inside of cell)

TM intracellular zeta chain dimer

V, D, J, C region domains (analogous to H chain of Ig)

V, J, C region domains (analogous to L chain of Ig)