Modulation of concanavalin A-induced, antigen-nonspecific regulatory cell activity by leu-enkephalin and related peptides.
We have developed a system in which human peripheral blood mononuclear cells (PBMC) stimulated with concanavalin A (Con A) can be examined for regulatory cell activity upon coculture with responder cells undergoing mitogenic proliferation. Low concentrations of Con A resulted in the induction of helper function, while higher concentrations of Con A induced suppressor activity in the PBMC population. However, for each individual donor a particular concentration of Con A can be found at which point no regulatory cell activity is observed. This "balance point" provides a set of conditions under which the ability of an immunomodulator to up-regulate or down-regulate the system can be studied. The ability of leu-enkephalin to positively or negatively regulate an immune response was examined under these circumstances. The addition of leu-enkephalin to cultures stimulated by Con A at this balance point enhanced both suppressor cell (Ts) and helper cell (Th) activity in a concentration-dependent manner. The induction of Ts activity displayed a bimodal response at concentrations between 10(-12) to 10(-13) M and 10(-9) to 10(-10) M, while the induction of Th activity was consistently observed at 10(-11) M. Similar effects were seen with either of the peptides Tyr-Gly and Tyr-Gly-Gly, corresponding to the first two and three amino acids of the N-terminal ends of the enkephalins. Th activity was consistently enhanced at 10(-13) M Tyr-Gly-Gly and 10(-14) M Tyr-Gly. This suggests that leu-enkephalin may either positively or negatively regulate immune responses and that the intact leu-enkephalin molecule is not required for these effects.
Sizemore
R C
RC
Imreg, Inc., New Orleans, Louisiana 70112.
Dienglewicz
R L
RL
Pecunia
E
E
Gottlieb
A A
AA
D003208:Concanavalin A / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004336:Drug Antagonism; D004743:Enkephalin, Leucine / Q000494:pharmacology*; D006801:Humans; D007109:Immunity / Q000187:drug effects; D066298:In Vitro Techniques; D009842:Oligopeptides / Q000494:pharmacology; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D006377:T-Lymphocytes, Helper-Inducer / Q000187:drug effects; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects
D009842:Oligopeptides; D003208:Concanavalin A; C044757:tyrosyl-glycyl-glycine; D004743:Enkephalin, Leucine