E arly pro-b cell: dj rearrangements on both chromosomes. S igh chain rearrangement: vj and then lambda or kappa lc on igm surface= immature b cell. Heavy chain rearrangement: dj =pro b cell (limited capacity for self renewal) then vdj (mu. 1-repertoire assembly in bone marrow (clone and diversity) 2-negative selection (remove those that bind to self ) 3-positive selection (select immature cells to become mature in secondary lymphoid tissue) 4-search for infection (recirculation of mature cells in lymph/blood/tissue) 5,6-find and attack infection as functioning effector cells (activate and expand; pathogen- C hapter 6: development of b lymphoc ytes. Hc made)=pre b cell expresses mu chain with igm expressed on surface. Development is stimulated by stromal cells=microenvironment for maturation. P roductive and non-productive rearrangements addition of n and p nucleotides causing frame shifts (50% thrown out!)) expression required to inhibit apoptosis.