Modulation of lymphocyte motility by beta-endorphin and met-enkephalin

The opioid peptides, beta-endorphin and met-enkephalin, have been shown to affect the immune system, resulting in either enhancement or suppression of immune response. However, the mechanism of the immunomodulatory effects and the immune cells that are affected by the opioid peptides are unclear. Early studies have provided evidence for their influence on granulocytes, monocytes and lymphocytes. In this study, the effect of beta-endorphin and met-enkephalin on the motility of lymphocyte subpopulations was examined. beta-Endorphin, depending on the concentration tested, has only slight enhancing or inhibitory effect on the motility of spleen lymphocytes; interestingly, met-enkephalin inhibited their motility. However, both beta-endorphin and met-enkephalin have a similar effect on the motility of separated spleen T and B lymphocytes, in that the motility of B lymphocytes was enhanced by both opioid peptides whereas the motility of T lymphocytes was inhibited. In contrast to the inhibitory effect of beta-endorphin and met-enkephalin on mature spleen T lymphocytes, the motility of thymocytes was enhanced by both opioid peptides. The results from this study suggest that the interaction of beta-endorphin and met-enkephalin with lymphocytes is complex and intricate.