Effects of dynorphin on the PHA-induced lymphocyte proliferation in vitro

The effect of the opioid peptide dynorphin (DYN) on PHA-induced lymphocyte proliferation has been evaluated in the present study. A significant increase in PHA-induced lymphocyte activation was observed when DYN was added to cultures 48 hr after the mitogenic stimulation. This effect occurred at suboptimal (3.12 and 6.25 micrograms/ml) PHA concentrations and at DYN doses ranging from 10(-9) to 10(-12) M. Conversely, DYN did not affect the lymphocyte blastogenic process either when added before, or simultaneously or after intense PHA (12.5 micrograms/ml) stimulation. Naloxone preincubation did not modify the above described effects. Results suggest that DYN might play a role in neuroendocrine regulation of the lymphocyte blastogenic process.