INTERACTIONS BETWEEN B-LYMPHOCYTES AND NK CELLS

The ability of natural killer (NK) cells to secrete lymphokines confer s upon them the potential to regulate cell types via mechanisms other than direct cytotoxicity. During the past few years increasing evidenc e has been accumulating to show that NK and B cells can interact produ ctively. First, NK cells cocultured with B cells can induce them to in itiate polyclonal Ig secretion. This help is mediated by a soluble fac tor (or factors) that appears to be different from any known cytokine. Second, preactivated B lymphocytes can induce NK cells to produce gre ater amounts of IFN-gamma via an interaction that requires direct cell contact. Third, in contrast to previous suggestions, NK cells do not have the ability to kill primary B lymphocytes regardless of their sta ge of differentiation. Evaluation of the in vivo relevance of these in teractions revealed that activated NK cells can increase the IgG2a res ponse to a specific protein antigen. Without activation, NK cells neit her enhance nor inhibit B cell responses to antigens. The deviation of the isotype distribution may allow increased NK cell specificity for certain pathogens by enhancing antibody-dependent cytotoxicity.