Inhibition of NK and K cell function by phenothiazines

Several phenothiazines have been shown to inhibit NK cell-mediated cytotoxicity (NKC) and antibody-dependent cell-mediated cytotoxicity (ADCC) effected by human peripheral blood lymphocytes. Of those tested, chlorpromazine was found to inhibit at the lowest concentration (5 microM) with a 90% inhibition at 10 microM for NKC and 70% inhibition for ADCC. Pre-incubation of either effector or target cells with chlorpromazine did not provide any evidence of inhibition in subsequent cytotoxicity assays. The data for chlorpromazine in particular may be of clinical significance. In vivo inhibition would presumably require the presence of the drug since preincubation did not produce inhibition of NK or K cell function.