Competence and competition: the challenge of becoming a long-lived plasma cell.

Plasma cells provide humoral immunity. They have traditionally been viewed mainly as short-lived end-stage products of B-cell differentiation that deserve little interest. This view is changing, however, because we now know that plasma cells can survive for long periods in the appropriate survival niches and that they are an independent cellular component of immunological memory. Studies of the biology of plasma cells reveal a mechanism of intriguing simplicity and elegance that focuses memory provided by plasma cells on recently encountered pathogens while minimizing the 'fading' of memory for pathogens encountered in the distant past. This mechanism is based on competition for survival niches between newly generated plasmablasts and older plasma cells.