RESUMO
Mononuclear cells separated from heparinized fresh venous blood of healthy male bloodclonors by means of Ficoll- Hypaque density gradient centrifugation were subjected to petri dish adhesion and nylon wool-column separation to obtain monocytes and T lymphocytes of high purity, respectively. Antigen- presenting capability of the monocytes, as reflected by T lymphocyte proliferation, was assayed after the monocytes had been preincubated with PPD (purified protein derivative, end concentration12.5 ?g /ml ) and methione enkephalin (M-Enk) in defferent concentrations for 24 hours at 37 ℃ in a humidified incubator containing 5% CO_2. It was shown that the antigen-presenting capability of the monocytes was markedly enhanced by M-Enk when its concentration was from 10 ~(-10) M to 10~(-14) M(close to the normal serum concentration of M-Enk), and this effect of M-Enk could be cancelled if the monocytes had been pretreated with 10~(-6) M naloxone for 30 min before addition of PPD and M-Enk, suggesting that the effect of M-Enk in these concentrations was mediated through the opioid receptors on the monocytes. M-Enk in high concentrations (10~(-4) M-10~(-6)), however, was found to inhibit th'e antigen- presenting capability significantly and this inhibition could not be cancelled by pretreatment of the monocytes with naloxone.