Immunophenotypic changes in human leukocytes induced by two heat-killed mycobacterial vaccines

Abstract

Previous research studies had emphasized the role of mycobacteria in modulating immune responses and in promoting the interaction between innate and adaptive immunity. The possession of a selected antigenic profile by fast-growing mycobacteria, has driven the evaluation of mycobacterial vaccines as adjuvant therapy in the treatment of infections, allergy, asthma and cancer. Despite the wide implication of mycobacteria in enhancing the immune recognition and elimination of pathogens, the nature of host cellular receptors regulated by these organisms remains to be elucidated. The aim of this study was to investigate the effects of two fast-growing mycobacteria, Mycobacterium vaccae and Mycobacterium obuense on the expression of a battery of cellular receptors in human peripheral blood leukocytes. Our results clearly demonstrate the ability of the two evaluated vaccines to i) up-regulate the expression of costimulatory and antigen-presentating molecules on human monocytes; ii) enhance the expression of complement receptors and Fcreceptors on phagocytic cells and iii) induce lymphocyte proliferative responses in peripheral blood mononuclear cells. The data obtained in this study highlighted potential mechanisms for some of the already known activities of heat-killed mycobacterial vaccines and strongly suggested the implication of different categories of leukocyte receptors in mediating the spectrum of immunomodulatory activities of mycobacteria.