Making sense of plasma cell heterogeneity.

Plasma cells (PCs) are essential for the quality and longevity of protective immunity. The canonical humoral response to vaccination involves induction of germinal centers in lymph nodes followed by maintenance by bone marrow-resident PCs, although there are many variations of this theme. Recent studies have highlighted the importance of PCs in nonlymphoid organs, including the gut, central nervous system, and skin. These sites harbor PCs with distinct isotypes and possible immunoglobulin-independent functions. Indeed, bone marrow now appears unique in housing PCs derived from multiple other organs. The mechanisms through which the bone marrow maintains PC survival long-term and the impact of their diverse origins on this process remain very active areas of research.