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.