Interactions Between B Lymphocytes and NK Cells: An Update

The major role of NK cells has traditionally been assigned to their cytotoxic activity both against tumor cells and against virus-infected cells. Only recently has there been greater appreciation for their more diverse functions. The interaction between NK and B cells is unique in that NK cells have not been reported to kill B cells, allowing, therefore productive interactions between the two cell types. In this review we have focused on the ability of NK cells to influence the two major functions of B cells, their ability to secrete antibodies and to present antigen to T cells. This review provides the definitive evidence obtained from in vitro experiments that NK and B cells can interact productively in both directions. In addition, much progress has been made toward identification of the receptor–ligand pairs required for the interaction. This review also points out that whereas there is evidence for similar interactions to occur in vivo, unraveling the mechanisms by which this occurs is more challenging due to the many players involved. For this same reason we have focused the review in the mouse system which is more amenable to in vivo manipulation. We realize that much insights derived from work with human cells should be informative, but complete correlation with findings between the two system is beyond the scope of this review.