The lymphocytes of splenic marginal zones: a distinct B-cell lineage

In a recent article on B-cell development Klinman and his colleagues asked the question ‘Do B cells exist as separate lineages?’. Studies of B cells in rat spleen support on affirmative answer to this question. Here Ian MacLennan and his colleagues discuss the nature, function and origins of a mayor population of B cells in human and rat spleens which populate the marginal zones, comparing them with recirculating lymphocytes found in the follicles of all secondary lymphoid tissue.