IMMUNOMODULATORY PROPERTIES OF DIAZEPAM-BINDING INHIBITOR - EFFECT ONHUMAN INTERLEUKIN-6 SECRETION, LYMPHOCYTE-PROLIFERATION AND NATURAL-KILLER-CELL ACTIVITY IN-VITRO

We have examined the influence of diazepam binding inhibitor (octadeca neuropeptide, DBI33-50) on cell mediated immune responses including LP S-stimulated monocyte IL-6 secretion, PHA induced lymphocyte prolifera tion and NK cell function in humans. All studies were performed in vit ro on isolated human peripheral blood mononuclear cells in the absence or presence of synthetic DBI33-50. It has been shown that DBI33-50, i n concentration between 10(-6)-10(-8) M, enhances the LPS-induced secr etion of IL-6, as determined by specific bioassay for this monokine. O n the other hand DBI33-50 (10(-6)-10(-12) M), had no significant effec t on either PHA-induced lymphocyte proliferation or NK cell function. This data suggests a possible immunomodulatory role for DBI33-50 as an endogenous neuropeptide, which stimulates IL-6 secretion by human mon ocytes.