Induction of activation antigens on human natural killer cells mediated through the Fc-gamma receptor.

NK cells, defined here as lymphocytes bearing the CD16 Ag found on the NK cell Fc-gamma receptor (FcR), are known to enter a proliferative and activated state in response to stimulation with IL-2 as assessed by clonal expansion, short-term DNA synthesis, and de novo expression of lymphocyte-associated activation Ag. We have found that the FcR of NK cells acts as a signaling pathway through which IL-2-dependent activation may be greatly enhanced, allowing for more rapid induction of activation Ag and recruitment of an increased percentage of cells expressing surface markers of cellular activation. FcR-interactive agents, such as solid phase immobilized immune complexes or cross-linked CD16-specific mAb, work synergistically with rIL-2 to elicit a rapid expression of IL2R and transferrin receptors on greater than 50% of purified NK cells as early as day 3 of culture. IL-2 or FcR-interactive stimuli alone were weak or ineffective stimulators by comparison. In contrast to the induction of de novo activation Ag, DNA synthesis was elicited by IL-2 alone, but was not substantially or consistently enhanced by the subsequent addition of FcR-interactive stimuli.

Restricted immunoglobulin variable region gene usage by normal Ly-1 (CD5+) B cells that recognize phosphatidyl choline.

5-15% of lymphocytes in the peritoneums of normal adult B10.H-2aH-4bp/Wts (2a4b) mice are CD5+ (Ly-1) B cells that recognize phosphatidyl choline (PtC), a phospholipid component of all mammalian cells. We produced a set of IgM-secreting hybridomas from the peritoneal cells of normal, adult 2a4b mice. We found that this set of hybridomas shows a similarly high frequency of antibodies specific for PtC (21 of 86) that also react with bromelain-treated mouse erythrocytes. Restriction fragment analysis of Ig gene rearrangements and analysis of expressed Ig idiotypes reveal that these cells use a restricted set of variable region genes to generate the PtC-specific antibodies. The Ig genes used by the PtC-specific hybridomas appear to be the same as those found in the PtC-specific Ly-1 B cell lymphomas, CH27 and CH34.

Selective inhibition of natural killer activity by the monoclonal antibodies OKT10 and VEP10 at the single cell level.

The monoclonal antibodies, VEP10 and OKT10, which have been shown to recognize determinants on human natural killer (NK) cells, inhibit large granular lymphocyte (LGL) NK activity against K562, MOLT4, and CEM tumor target cells in the single cell conjugate agarose assay. Inhibition of NK activity by monoclonal antibodies was expressed independently of effector-target cell binding, as inhibitory activity could be demonstrated when the monoclonal antibodies VEP10 and OKT10 were added to preformed conjugates or to the LGLs and targets prior to the binding event. In addition, this inhibition was exerted on the effector cell and not the target cell since VEP10 and OKT10 did not react with determinants on K562 target cells. Furthermore, the 4F2 monoclonal antibody, which reacted with determinants on the LGL and all of the targets used, effected no inhibition of NK activity. Inhibition of killing by OKT10 and VEP10 was specific to endogenous NK activity since the same antibodies did not inhibit antibody-dependent cellular cytotoxicity (ADCC), mixed lymphocyte-generated NK, or cytotoxic T lymphocyte (CTL) activities.