Endocrine control of the immunosuppressive activity of the submandibular gland

Abstract

Extracts of the submandibular gland (SMG) of rats contain fractions that stimulate the in vitro proliferation of Con A-treated lymphocytes. One of the stimulatory fractions was also shown to induce in vivo immunosuppression in rats and mice in several experimental models. Since many other biologically active factors of the SMG had been found to be hormone dependent, we investigated the effects on the immunosuppressive factor of hypophysectomy (Hx) and of hormonal reconstitution in male Fischer rats. Hx induced a marked atrophy of the SMG together with an almost complete disappearance of both the in vitro lymphocyte-stimulating activity and the in vivo immunosuppressive activity, the latter assayed with the contact sensitivity reaction in mice. The treatment of the Hx rats with pituitary hormones demonstrated that prolactin (PRL), thyroid stimulating hormone (TSH), and luteinizing hormone (LH) induced a significant reconstitution of these biological activities, growth hormone led to the recovery of the lymphocyte-stimulating activity but not of the immunosuppressive activity, while follicle-stimulating hormone, and adrenocorticotropic hormone did not induce any recovery of these biological activities. In view of the positive results obtained with TSH and LH further experiments were done to compare the effects of thyroid and sex hormones with those of PRL. The results demonstrated that testosterone and thyroid hormones induced significant recovery of the lymphocyte-stimulating and the immunosuppressive activity. The combination of these two hormones with PRL produced the most effective results. On the other hand, estrogens and progesterone had no significant effects. These results confirm the effectiveness of androgens and thyroid hormones in stimulating the production of biologically active factors by the SMG. Moreover, they demonstrate that PRL, a hormone not previously considered to increase the activity of the SMG, stimulates the production of immunoregulatory factors in Hx animals.