Describe the six functionally distinct phases of B-cell development.

(1) Repertoire assembly: Bone marrow expression of diverse B-cell receptors. (2) Negative selection: Modification, elimination or inactivation of autoreactive B cells. (3) Positive selection: Selection of a small subset of immature B cells to become mature B cells in secondary lymphoid organs. (4) Searching for infection: Patrolling for infectious material by recirculating continuously between lymph, blood and secondary lymphoid organ compartments. (5) Finding infection: B cells become activated by antigen in secondary lymphoid tissues and then undergo clonal expansion. (6) Attacking infection: B cells differentiate into plasma cells and memory cells in secondary lymphoid tissues.