Peripheral B cell survival

Recent findings suggest that lymphocyte survival is a continuous active pro cess and support the role of B cell receptor engagement in B cell survival. In this context the conflict of survival interests between the diverse B c ells gives rise to a pattern of interactions which mimics the behavior of c omplex ecological systems. In response to competition lymphocytes modify th eir survival requirements and diverge to occupy different immunological nic hes through differentiation. Thus naive and memory-activated B cell populat ions show independent homeostatic regulation. We discuss how niche differen tiation allows the coexistence of different cell types and guarantees both repertoire diversity and efficient immune responses.