Immunomodulating Properties of Corticotropin-Releasing Factor

Abstract

Corticotropin-Releasing Factor (CRF) is a low molecular weight peptide hormone (containing 41 amino acid residues) originally identified in the hypothalamic extracts of the ovine brain (Vale et al., 1981). It is now generally believed that a reciprocal relationship exists between the neuroendocrine system and the immune system (Singh, 1990). Based upon our recent observation that ¹²⁵I-CRF has specific binding sites on human peripheral blood immunocytes (Singh and Fudenberg, 1988), we hypothesized an immunoregulatory role for this neuropeptide (Singh, 1989 and 1990). In this respsect, our current research (Singh, 1989; Singh et al., 1990; Singh and Leu, 1990) showed that CRF is a stimulator of certain immune functions in vitro: (i) stimulation of lymphocyte proliferation in the absence or presence of T cell mitogens, e.g. concanavalin A and phytohemagglutinin which can be blocked specifically by the CRF-antagonist; (ii) increased expression of interleukin-2 receptor (IL-2R) antigen on T cells; and (iii) induction and enhancement of production of interleukin-1 (IL-1) and interleukin-2 (IL-2). Our newer data, as presented in this report, demonstrate that CRF is also a stimulator of natural killer (NK) cell activity but it has a suppressive effect on the production of antibodies or immunoglobulin G (IgG) in vitro.