title: Interleukin-6 induces early gamma interferon production in the infected lung but is not required for generation of specific immunity to Mycobacterium tuberculosis infection.
abstract: Immunity to Mycobacterium tuberculosis is dependent upon the generation of a protective gamma interferon (IFN-gamma)-producing T-cell response. Recent studies have suggested that interleukin-6 (IL-6) is required for the induction of a protective T-cell response and that IL-4 may suppress the induction of IFN-gamma. To evaluate the role of the cytokines IL-6 and IL-4 in the generation of pulmonary immunity to M. tuberculosis, IL-6 and IL-4 knockout mice were infected with M. tuberculosis via aerosol. The absence of IL-6 led to an early increase in bacterial load with a concurrent delay in the induction of IFN-gamma. However, mice were able to contain and control bacterial growth and developed a protective memory response to secondary infection. This demonstrates that while IL-6 is involved in stimulating early IFN-gamma production, it is not essential for the development of protective immunity against M. tuberculosis. In contrast, while the absence of IL-4 resulted in increased IFN-gamma production, this had no significant effect upon bacterial growth.
authors.affiliation: Mycobacterial Research Laboratories, Department of Microbiology, Colorado State University, Fort Collins, Colorado, 80523, USA. B.Saunders@centenary.usyd.edu.au
authors.forename: B M
authors.initials: BM
authors.lastname: Saunders
authors.forename: A A
authors.initials: AA
authors.lastname: Frank
authors.forename: I M
authors.initials: IM
authors.lastname: Orme
authors.forename: A M
authors.initials: AM
authors.lastname: Cooper
mesh_terms: D000818:Animals; D007111:Immunity, Cellular; D007156:Immunologic Memory; D007371:Interferon-gamma / Q000096:biosynthesis*; D015847:Interleukin-4 / Q000235:genetics / Q000276:immunology*; D015850:Interleukin-6 / Q000235:genetics / Q000276:immunology*; D008168:Lung / Q000276:immunology / Q000382:microbiology; D051379:Mice; D018345:Mice, Knockout; D014397:Tuberculosis, Pulmonary / Q000276:immunology*
chemical_list: D015850:Interleukin-6; D015847:Interleukin-4; D007371:Interferon-gamma