Inhibition of antigen specific lymphocyte proliferation and cytokine stimulation by peptidomimetic opioid compound

In sequel to our preliminary observations with peptidomimetic opioid compounds, we have further investigated immunomodulatory activity of one peptidomimetic compound (Tyr-NH-CH₂-CH₂-O-Phe-NH₂) with peripheral blood mononuclear cells (PBMCs) of healthy volunteers/tuberculosis patients. This peptidomimetic compound was evaluated for its effect on purified protein derivative (PPD) stimulated lymphocyte proliferation in vitro, production of Th1 and Th2 cytokines by ELISA and ribonuclease protection assay. Our study shows the immunosuppressive potential of above synthetic peptidomimetic compound. This compound inhibited PPD stimulated human lymphocyte proliferation and this inhibition was reversed by opioid receptor antagonist, naloxone. Its immunosuppressive effect was further demonstrated by inhibition of interleukin-9 (IL-9), IL-10 but failed to influence IL-2, IL-15 and interferon-γ (IFN-γ) in PPD stimulated human PBMCs.