Interleukin-6 regulates the phenotype of the immune response to a tuberculosis subunit vaccine

Authors


Dr R. Appelberg, Laboratory of Microbiology and Immunology of Infection, Institute for Molecular and Cell Biology, University of Porto, Rua do Campo Alegre 823, 4150–180 Porto, Portugal. E-mail: rappelb@ibmc.up.pt

Summary

We investigated the role of interleukin-6 (IL-6) in the development of the immune response to a subunit vaccine against tuberculosis consisting of the culture filtrate proteins of Mycobacterium tuberculosis emulsified in the adjuvant dimethyldioctadecylammonium bromide (DDA). C57Bl/6 mice immunized with this vaccine developed a strong T helper 1 (Th1) response characterized by an increased production of interferon-γ (IFN-γ) secreted by CD4+ T cells. Neutralization of IL-6 during in vivo priming resulted in marked reduction in the ability of T cells to secrete IFN-γ and IL-2 and to proliferate. IL-6 gene-disrupted mice primed with the vaccine showed a decrease in the number of IFN-γ-producing cells and an increase in IL-4-secreting cells as compared to control mice. In contrast, neutralization of IL-6 during a boost of the vaccine in previously primed mice did not affect the development of IFN-γ-producing cells but still increased the number of IL-4-producing cells. Our work shows that IL-6 plays a major role in the priming but not in the later expression of a Th1 response to a tuberculosis vaccine.

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