•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.