A possible role for protein kinase C activity but not cyclic nucleotide-dependent protein kinases in human natural killer cell lytic activity.

Recent evidence suggests that a Ca++, phospholipid, diacylglycerol-dependent protein kinase, protein kinase C, plays a role in the activation of cytotoxic T lymphocytes by target cells. In this investigation we have examined the role of protein kinase C in human NK cell-mediated cytolysis of K-562 cells. The protein kinase C inhibitor, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) inhibited human NK cell-mediated cytolysis in a dose dependent manner. On the other hand, N-(2-guanidinoethyl)-5-isoquinolinesulfonamide (HA1004), a specific inhibitor of cyclic nucleotide dependent protein kinases had no effect on human NK cell-mediated cytolysis of K562 cells. There is little or no effect on protein synthesis or N-glycosylation activity in human NK cells by H-7. The relative inhibitory ability of the two inhibitors suggest that protein kinase C, acting synergistically with Ca++ mobilization, plays a role in the early stages of human NK cell-mediated cytolysis of K562 target cells.

Modulation of human polymorphonuclear leukocyte IgG Fc receptors and Fc receptor-mediated functions by IFN-gamma and glucocorticoids.

Human polymorphonuclear neutrophils (PMN) normally express two distinct types of IgG Fc gamma R, the 40-kDa Fc gamma R referred to as Fc gamma RII and the low affinity 50- to 70-kDa Fc gamma R designated Fc gamma RIII. A third type of Fc gamma R, the 72-kDa high affinity receptor known as Fc gamma RI, is also detectable on PMN that have been activated by IFN-gamma. Using mAb that discriminate among the three known types of Fc gamma R, we examined the effects of IFN-gamma and glucocorticoids on human PMN Fc gamma R expression. We also studied effects of IFN-gamma and the synthetic glucocorticoid dexamethasone (DEX) on antibody-dependent cytotoxicity (ADCC) of chicken erythrocytes and phagocytosis of IgG-coated ox RBC by human PMN. In 20 donors studied, we found that treatment of PMN with 400 U/ml IFN-gamma induced a 9- to 20-fold increase in the number of Fc gamma RI sites per cell, and DEX inhibited this induction of Fc gamma RI by 39 to 73%. Similarly, DEX significantly reduced the IFN-gamma stimulation of ADCC and phagocytosis. IFN-gamma had no effect on expression of Fc gamma RII or Fc gamma RIII. Fc gamma RI and Fc gamma RII expression was unaltered by 24 h of treatment with DEX alone, but Fc gamma RIII expression was sometimes increased by about 20% on PMN cultured with DEX. Nevertheless, we found a small but significant inhibition of ADCC and phagocytosis by 200 nM DEX. Our results indicate that Fc gamma RI plays a major but not exclusive role in the regulation of ADCC and phagocytosis by IFN-gamma and DEX.