BIOL 1010U Lecture Notes - Immunoglobulin Class Switching, Subset, Cd24
Document Summary
Hematopoietic stem cells (hsc) in bone marrow are source of all blood cell lineages. Ability to self renew = long term reconstitution. Diff due to loss of reconstitution and differentiation potential (ex:mpp can differentiate but not self renew: antigen independent differentiation. Generate large pool of b lymphocytes with unique antigen receptor (diversity generator) (bone marrow) Weed out b cells that react against self (bone marrow and peripheral lymphoid organs, spleen: clonal selection. Antigen exposure selects few b cells to mount an immune response. Cd 19 marker of beginning differentiation (only il-7 does this alone) Common lymphoid progenitor (clp) expresses il-7r (last multipotent progenitor) Pre-pro b cells-(committed) needs e2a and ebf gene expression (1st ig gene rearrangements) Accessibility hypothesis all rearrangeable genes cant be acted upon by recombinase machinery b/c of chromatin strucute constraints. Constrains can be removed by enhancers/promoters and regulated by cis acting sequences. Rags recognize and cleave recombination signal sequence (rss) associated with rearranging gene segments.
