The immunomodulatory effects of prolactin and conventional lymphocyte mitogens on rat Nb 2 lymphoma cells

Rat Nb 2 lymphoma cells, (derived from T-cells), have a high density of receptors for lactogenic hormones. In this study, Nb 2 cells cultured for three days with rat prolactin (0.625-100 ng/ml) exhibited dose-dependent stimulation indices. Attempts to induce similar proliferative responses in Nb 2 cells using plant lectins which are conventional T-cell mitogens, failed at concentrations normally stimulatory for rat lymphocytes. When Nb 2 cells were simultaneously incubated with lectin plus 10 ng/ml prolactin, a dose-dependent suppression of the stimulatory effects of prolactin was observed. However, the alteration of the prolactin response was different for each mitogen. If Nb 2 cells were exposed to one of the plant lectins for one hour prior to a 3-day incubation with prolactin, no such suppression was observed. Therefore, suppression of the response to prolactin by conventional lymphocyte mitogens appears to be dependent upon continuous exposure to these mitogens.