Enhancement of the generation of cytotoxic T cells by endogenous opiates.

Previous reports have shown that endogenous opiates (beta-endorphin and met-enkephalin) have effects on cells of the immune system at physiologic concentrations. Using murine spleen cells, we herein report that beta-endorphin and met-enkephalin can enhance the generation of cytotoxic T lymphocytes (CTLs) at suboptimal concentrations of alloantigen in a one-way mixed lymphocyte culture (MLC). This enhancement is seen at levels ranging from 2.9 X 10(-8) M to 2.9 X 10(-14) M and 1.45 X 10(-6) M to 1.45 X 10(-12) M for beta-endorphin and met-enkephalin, respectively. This enhancement can be partially blocked by naloxone at 10(-7) M. Furthermore, the simultaneous addition of met-enkephalin and beta-endorphin does not increase the enhancement of CTL generation by either opiate peptide alone suggesting that they are acting through the same receptor. This report gives added proof for the regulatory-loop theory between the neuroendocrine and immune systems.