The Herzenberg lab has been a pioneer in B-cell research. Professor Leonore Herzenberg is considered one of the preeminient B cell experts in the field.

Some time ago, we pointed out that the crucial role of the immune system in protecting organisms against invasion by pathogens makes it very difficult for evolution to "experiment" with new avenues of immune responsiveness unless such experimentation is undertaken without interfering with ongoing protection offered by the existing system. To accomplish this goal, we suggested that the evolution of the immune system occurred in layers, with a new layer being put into place before the old layer is superannuated. Ultimately, one could expect the new and the older layer to adjust to each other, with some functions remaining in the old layer in a position to back up and co-operate with the newly evolved functions in the latest layer. Since each layer in such a system would have to be capable of developing and functioning on its own while a new layer is "under construction", it would be difficult (although not impossible) to derive all layers from a single developmental lineage. Thus, just as ontogeny recapitulates phylogeny, one could expect to find that the highly-evolved mammalian immune system is composed of functionally distinct layers, embodied in separate developmental lineages, that recapitulate the progressive evolution of phenotype and function.

Since the B-1 cells arise earliest in development and display many of the characteristics of primitive B cells such as those in the chicken (e.g., neonatal development, self-replenishment in adults, feedback regulation of development, CD5 expression), we suggested that B-1 cells represent the early evolutionary layer(s) (of the immune system whereas B-2 cells represent the more highly-evolved later layers.

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