Immune-modulating Effects of Mycobacteria

Abstract

Abstract Background:Several species of Mycobacterium have been identified as having the ability to modulate immune responses, even as heat-killed preparations. Our goal was to identify mycobacteria that could potentially act in a safe and non-toxic immune-modulating effect by promoting the production of specific chemokine and cytokine responses with a potential application for impacting the microbiome. We relied on the following Mycobacterium strains: M. smegmatis, M. agri, M. phlei, M. tokaiense, M. brumae, M. aurum, and M. obuense. Results:M. smegmatis and M. agri were the most effective in inducing immune responses in cultured peripheral blood mononuclear cells (PBMC) manifested by extracellular productions of the cytokine IL-6, as well as the chemokines IL-8, MIP-1α and MIP-1β. Correlation analyses and immune challenges to the bacterial mixtures showed that while cytokine and chemokine responses to M. smegmatis and M. agri were similar, they were different from responses to either B. subtilis or phytohemagglutinin (PHA) resulting in distinct patterns of extracellular cytokine and chemokine productions. Our results suggest that Mycobacterium strains and B. subtilis activated distinct immune response pathways and have different effects on the immune system.Conclusions:We identified several Mycobacterium species as well as B. subtilis as the most efficient immune-modulating agents. Distinct immunomodulatory properties of multiple species may have potential implications for immunotherapy of cancer as well as treatments of various immune-deficiency disorders. Our methodology for comparing immune responses of bacterial preparations may provide a useful tool for studying immune effects of pathogenic and non-pathogenic bacteria.