DIFFERENTIAL-EFFECTS OF GROWTH-HORMONE AND PROLACTIN ON MURINE T-CELLDEVELOPMENT AND FUNCTION

DW/J dwarf mice have a defect in their anterior pituitary and are defi cient in growth hormone (GH) and prolactin (PRL). These mice have been demonstrated previously to have a deficiency in CD4/CD8 double-positi ve thymocytes, which could be corrected by treatment of these mice wit h recombinant human GH. Since PRL has been implicated in T cell functi on and human GH can interact with the PRL receptor, DW/J dwarf mice we re treated with either ovine GH (ovGH) (20 mug/d) or ovine PRL (ovPRL) (20 mug/d). The ovine hormones can only bind their own specific recep tors in the mouse. After several weeks of treatment, it was found that these two hormones produced markedly contrasting effects on T cells. Phenotypic analysis of the lymphoid organs was performed by flow cytom etry and the functional capability of the peripheral T cells was asses sed by immunizing the mice and determining the extent of antigen-speci fic proliferation of T cells obtained from the draining lymph nodes or by determining splenic mitogen responses. The results indicated that ovGH administration to dwarf mice resulted in significant increases in thymic cellularity yet had little effect on peripheral T cell respons es. In contrast, the administration of ovPRL resulted in a further dec rease in thymic cellularity when compared with untreated dwarf mice. N o thymic effects of either ovGH or ovPRL administration were detected on the normal +/? counterparts. However, ovPRL administration resulted in a significant increase in the number and function of antigen-speci fic peripheral T cells in both immunized dwarf and +/? mice. The adjuv ant effects of PRL occurred even though the mice also received complet e Freund's adjuvant. These results suggest that neuroendocrine hormone s may act in concert in T cell development. GH appears to promote thym ocyte proliferation, while PRL appears to decrease thymus size and yet augment the number and function of antigen-specific T cells in the pe riphery.