Prolactin gene expression in human thymocytes.

Recent evidence suggests that lymphocytes produce prolactin (PRL). Here, we report the cDNA cloning and expression of PRL from normal human thymocytes. Sequence analysis showed that the thymocyte cDNA encodes a 23 kDa protein which is identical to pituitary PRL. RNA blot analysis showed that the thymocyte PRL mRNA is approximately 170 nucleotides larger than the pituitary PRL message. PRL message was also detected in several non-pituitary human cell lines including Jurkat T, HeLa, and JEG cells. Furthermore, PRL gene expression in JEG cells was inhibited by glucocorticoid treatment. Our data support the hypothesis that PRL is a T cell-derived cytokine.