Synthesis of a prolactin-like peptide by natural killer cells: positive regulation by CD16 and exogenous prolactin.

We have previously shown that Prolactin (PRL) activates the native and the in vitro acquired cytotoxicity and the DNA synthetic activity of Natural Killer (NK) cells. Here we show that the supernatant and the cell lysate of NK cells express a 35S-labelled 50 kDa peptide specifically immunostained by two different PRL-antisera. The supernatant of NK cells was biologically active in a Nb2 assay and the activity could be adsorbed by an anti-PRL antiserum. The production of the PRL-like peptide only occurred when NK cells were isolated through binding to immobilized immunocomplexes, the biological ligand for CD16, and was positively modulated by exogenous PRL. These results indicate that PRL, produced by NK cells following stimulation, may act in an autocrine fashion to maintain and/or activate the NK cell function.