Prolactin is a peptide hormone with effects on a number of target organs including the immune system. It has been shown that animals rendered hypoprolactinemic have impaired delayed hypersensitivity, impaired macrophage activation and altered secretion of gamma interferon (IFN). Using peripheral blood mononuclear cells (PBMC) and inducing the cells to produce gamma IFN with a range of inducers, we have studied the effects of a number of hormones on IFN production. Using cells from normal donors, we have found that prolactin in concentrations of 10(-8) M or greater, can significantly enhance the production of gamma IFN. The effect was dose related and was observed when lectins (PHA and Con A), but not anti CD3 antibodies, ionophones, or IL-2 were used to induce the cells. The presence of prolactin in concentrations above that encountered in the fetal bovine serum used to incubate the cells resulted in a doubling or more of the IFN produced. The tests were performed on 30 occasions with cells drawn from 21 individuals. On all but three occasions, yield enhancement was observed in the presence of prolactin. The mechanism of the effect was investigated, and genistein, a tyrosine kinase inhibitor, was found to abort the influence of prolactin on gamma IFN production. These studies indicate prolactin in physiological concentrations can enhance the production of gamma IFN from cells from normal donors.

Somatostatin (SMS) is a tetradecapeptide which can inhibit the secretion of a number of peptides produced by the endocrine or nervous systems. SMS 201-995 (octreotide) is a somatostatin analogue with very potent somatostatin activities. We have been investigating the effects of both SMS and octreotide on the production of human interferon (IFN). We obtained human peripheral blood mononuclear cells from normal donors and induced them to produce IFN in the presence or absence of a number of peptides possessing somatostatin activities. SMS and octreotide were shown to inhibit the secretion of INF-gamma but not IFN-alpha. Concentrations of 10(-6) M were shown to decrease yields when Concanavalin A or phytohemagglutin were used as the inducer. Higher concentrations had a progressively greater effect. No effects were observed on IFN-gamma production if interleukin 2, ionomycin, or various natural antigens were used to induce the cells. The 28-amino acid form of somatostatin had some effects on gamma IFN yields but the first 14-amino acid fragment of this peptide moiety did not. No effect of any of these compounds was observed on IFN bioactivity. These studies indicate SMS may have some regulatory action on the secretion of immunomodulators in vitro but the concentrations required are well above those encountered under physiologic circumstances, suggesting SMS may not play an important regulatory role governing such secretion in vivo.

Concentrations of hydrocortisone as low as 0.08 microgram/ml significantly reduced the yields of gamma-interferon (IFN-gamma) when phytohemagglutinin (PHA) or concanavalin A (ConA) were used as inducers; however, when staphylococcal enterotoxin A was utilized, higher concentrations (5.0 micrograms/ml) were required to achieve the same effect. Yields of interleukin-2 (IL-2) and lymphotoxin were also found to be sensitive to the effects of the steroids, but expressions of TAC antigen was not generally affected by these agents. In contrast to the effects of steroids on cell proliferation, lymphokine production remained suppressed after steroid withdrawal. Hydrocortisone appeared to influence the concentrations of cyclic nucleotides following lectin stimulation, but attempts to correct these alterations or to add exogenous IL-2 failed to restore lymphokine production to normal levels. Addition of the calcium ionophore A23187 partially restored IFN-gamma production. We conclude that the effects of corticosteroids on the yields of lymphokines, including IFN-gamma, are profound. The depression of lymphokine production appears to be associated with a number of alterations in the cell, including depression of protein synthesis, alterations in cyclic nucleotides, and diminution of the production of cofactors necessary for IFN-gamma production. Enhancement of the flux of calcium into the cell may restore some of the ability to produce IFN-gamma.

Summary Somatostatin (SMS), a naturally occurring peptide is known to inhibit the production of certain protein molecules and to diminish the ability of peripheral blood mononuclear cells to proliferate. We tested the effects of three forms of SMS on the bioactivity of both lymphotoxin (LT) and tumour necrosis factor (TNF). We also tested the effects of these agents on production of cytotoxins by peripheral blood mononuclear cells. We found the 28 amino acid form of SMS significantly enhanced the bioactivity of both LT and TNF (10-9 M concentration) when tested in mouse L cells. The 14 amino acid form of SMS enhanced LT (10-9 M concentration) activity but not TNF activity. The first 14 amino acid form of SMS-28 (amino terminal) did not affect bioactivity of the cytotoxin. In contrast, the naturally occurring 14 amino acid form of SMS (10-8 M concentration) significantly diminished production of cytotoxin by human peripheral blood mononuclear cells. Cytotoxin produced by the latter was shown to be a combination of both LT and TNF.

Gonadotropins--follicle-stimulating hormone (FSH), luteinizing hormone (LH), and human chorionic gonadotropin (HCG)--and the related agent thyrotropin were shown to enhance yields of interferon-gamma (IFN-gamma) from human peripheral blood mononuclear cells (PBMC) significantly when calcium ionophores (ionomycin or A23187) were used as inducers. The enhancement increased the IFN yields four- to eight-fold. Induction with other inducers, (such as lectins, interleukin-2 (IL-2), and anti CD3, was not associated with enhancement of the IFN yields by gonadotropins. Concentrations of gonadotropins associated with pregnancy (HCG) or menopause (FSH and LH) were able to enhance IFN-gamma yields. Addition of the gonadotropins to the cells after the ionophore gave the greatest degree of enhancement. Perturbation of the calcium messenger system or nonspecific stimulation of adenyl cyclase failed to influence the IFN yield enhancing effect of the gonadotropins. No effect of gonadotropins was observed on IFN bioactivity.