Natural killer cell cytotoxicity is not regulated by folic acid in vitro

Abstract

Objectives: Folate supplementation may be associated with an increased risk of developing several types of cancer and a derangement of immune function.Among the latter, Natural killer (NK) cells are involved in non–MHC-restricted natural immunity against malignant target cells. Abnormalities in NK cell number or function have been associated with a higher cancer risk. The aim of this studywas to study in vitro the possible effect of different concentrations of 5-methyltetrahydrofolic acid (5-MTHF) or folic acid on NK cell cytotoxic function, and expression of the stimulatory and inhibitory receptors KIRDL4, KIRDL3, and NKG2D. Methods: Volunteer-derived peripheral mononuclear cells (PBMC) and highly enriched NK cells (95% CD56þ CD16þ) were grown in folic acid free–RPMI 1640, supplemented either with folic acid or 5-MTHF (15–100 nM) during 72 h to 96 h. Results: No differences in the cytolytic activity of PBMC and enriched NK cells were observed. After 96 h of in vitro culture without folate or supplemented with FA or 5-MTHF (30 or 100 nM), there were no changes in the percentage of HPNK receptor-positive cells. Conclusions: Our data indicate that a high dose of 5-MTHF or folic acid does not influence NK cell function in vitro.