Mononuclear phagocyte accumulates a stearic acid derivative during differentiation into macrophages. Effects of stearic acid on macrophage differentiation and Mycobacterium tuberculosis control

Abstract

The fatty acid composition of monocytes changes substantially during differentiation into macrophages, increasing the proportion of saturated fatty acids. These changes prompted us to investigate whether fatty acid accumulation in the extracellular milieu could affect the differentiation of bystander mononuclear phagocytes. An esterified fatty acid derivative, stearate, was the only fatty acid that significantly increased in macrophage supernatants, and there were higher levels when cells differentiated in the presence of Mycobacterium tuberculosis H37Rv or purified protein derivative (PPD). Exogenous stearic acid enhanced the expression of HLA-DR and CD64; there was also accumulation of IL-12, TNF-α, IL-6, MIP-1 α and β and a reduction in MCP-1 and the bacterial load. These results suggested that during differentiation, a derivative of stearic acid, which promotes the process as well as the effector mechanisms of phagocytes against the mycobacterium, accumulates in the cell supernatants.