A BIOACTIVE 60-KILODALTON PROLACTIN SPECIES IS PREFERENTIALLY SECRETED IN CULTURES OF MITOGEN-STIMULATED AND NONSTIMULATED PERIPHERAL-BLOODMONONUCLEAR-CELLS FROM SUBJECTS WITH SYSTEMIC LUPUS-ERYTHEMATOSUS

We have evaluated the production of PRL by human peripheral mononuclea r cells (PBMNC) from normal subjects and patients with systemic lupus erythematosus (SLE). Conditioned medium prepared from basal and Con-A- stimulated PBMNC was assessed for the presence of PRL-like by its abil ity to stimulate growth of PRL-responsive Nb2 rat lymphoma cells. In t he presence or absence of Con-A, SLE PBMNC secrete significantly highe r (P < 0.001) amounts of bioactive PRL-like species than normal cells. Growth of Nb2 cells by conditioned medium was inhibited with specific antiserum to human PRL. Western blotting using a polyclonal antibody to human PRL revealed a single 60-kDa PRL-like species in both normal and SLE PBMNC extracts, the immunoreactivity of which was preferential ly found in SLE subjects. With the use of reverse transcription-PCR an expected 633-bp band was observed, and its similarity to pituitary PR L was further confirmed by Southern blot analysis with human PRL compl ementary DNA as a probe. We conclude that a high molecular mass PRL-li ke species is synthesized and secreted by PBMNC, and patients with SLE have an increased secretion of lymphocyte-derived PRL-like material.