Fig. 1.

Effect of prolactin and cortisol treatment on the functions of peripheral blood purified NK cells. (a) NK cells were tested in a 4-h ⁵¹Cr-release assay against K562 a human chronic myelogenous leukaemia cell line at 1 : 1, 5 : 1, 10 : 1, 25 : 1 and 50 : 1 effector : target cell ratio. Cells were treated with prolactin, cortisol, rhIL-2 or rhIL-15 for 16 h before assays or left untreated. The increase in ⁵¹Cr-release over baseline reflects the ability of a given stimulus to trigger the lytic machinery. Results are expressed as means of absolute values ± s.d. of six individual experiments. (b) NK cells were used after treatment with or without prolactin and cortisol: prolactin-enhanced and cortisol-inhibited NK cell cytotoxicity against the K562 cell line at an E : T ratio of 25 : 1. This experiment is representative of six performed with similar results; s.d. for all data were less than 5%. (c) Cytolytic activity after treatment of NK cells with increasing concentrations (0·25 µm, 0·5 µm, 1 µm, 2 µm and 4 µm) of prolactin or cortisol. Percentage of specific lysis was measured at an E : T ratio of 25 : 1 after 4 h. This experiment is representative of six performed with similar results; s.d. for all data was less than 5%.