•Gene rearrangement: Comparison in B cell and T
cell
•SIMILARITIES
•T cells have
almost identical strategies as B cells
•Use the same
enzymes
•Light chain ↔ TCRα(V, J) ; Heavy chain ↔ TCRß (V,
D, J)
•One productively
rearranged VDJ is expressed with surrogate chain(s) as soon as it is made
•The mature
receptor is required for further development and shutting down further
rearrangement
•
•DIFFERENCES
•Three separate
lineages of T cells: α:ß, γ:δ, and α:ß-NK
•Non productive
ß-chain VDJ can be rescued by subsequent rearrangement because of two
clusters of Dß and Jß upstream of
two Cß
èThe chances are higher for productive rearrangement of ß chain that for Ig heavy chain.
•B cells: Final assembly of an immunoglobulin leads to the cessation of
gene rearrangement and initiates further
differentiation
•T cells: rearrangement of V α continues until positive selection by
self-peptide: self-MHC complex
•RAGs are transcriptionally regulated by different enhancers and V
segments loci are differentially accessible
at chromatin level.