AUGMENTATION OF TNF-ALPHA PRODUCTION, NK CELL-ACTIVITY AND IL-12 P35 MESSENGER-RNA EXPRESSION BY METHIONINE-ENKEPHALIN

AIM: To study the host immune surveillance functions by the neuropepti de methionine enkephalin (met-enk). METHODS: To measure the effects of met-enk on NK activity, the production and gene expression of anti-tu mor cytokines tumor necrosis factor a (TNF-alpha) and interleukin-12 ( IL-12) in vitro and In vivo. RESULT: Met-enk promoted NK activity at 1 x 10(-8) - 1 x 10(-5) mol . L(-1), increased TNF-alpha production bot h in vitro and in vivo, and enhanced IL-12 p35 gene transcription afte r ip 0.1 mg kg(-1) for 6 d. CONCLUSION: The upregulating effects of me t-enk contribute to the host neuro-immunomodulating mechanism against tumors and invading antigens.