title: T-cell-independent granuloma formation in response to Mycobacterium avium: role of tumour necrosis factor-alpha and interferon-gamma.
abstract: We used Mycobacterium avium infection in severe combined immunodeficiency (SCID) mice to examine T-cell-independent mechanisms of inflammatory cell recruitment. SCID mice infected with a virulent strain of M. avium (TMC724) were able to recruit macrophages to sites of mycobacterial replication and formed organized and coherent granulomas in the absence of functional T cells. Phagocyte recruitment was almost totally ablated by neutralization of either tumour necrosis factor-alpha (TNF-alpha) or interferon-gamma (IFN-gamma) in vivo demonstrating that granuloma formation was dependent on the presence of these cytokines. This was concomitant with a reduction in the in situ cytokine mRNA levels otherwise induced in infected mice, for chemokines, pro-inflammatory and regulatory cytokines, including TNF-alpha, IFN-gamma, macrophage inflammatory protein-1 alpha, interleukin-1 beta (IL-1 beta) and IL-10. Furthermore, in vivo treatment of infected mice with anti-asialo GM-1 antisera, which depletes natural killer (NK) cells, prevented recruitment of inflammatory cells. In vitro studies confirmed that M. avium was able to elicit IFN-gamma from SCID spleen in a dose-dependent manner. These data show for the first time that secretion of IFN-gamma from NK cells can mediate a T-cell-independent pathway of granuloma formation and cellular infiltration in response to mycobacteria.
authors.affiliation: Department of Clinical Science, London School of Hygiene and Tropical Medicine, UK.
authors.forename: D
authors.initials: D
authors.lastname: Smith
authors.forename: H
authors.initials: H
authors.lastname: Hänsch
authors.forename: G
authors.initials: G
authors.lastname: Bancroft
authors.forename: S
authors.initials: S
authors.lastname: Ehlers
mesh_terms: D000818:Animals; D018929:Cell Culture Techniques; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D006099:Granuloma / Q000276:immunology* / Q000473:pathology; D007371:Interferon-gamma / Q000096:biosynthesis / Q000276:immunology*; D007694:Killer Cells, Natural / Q000276:immunology; D051379:Mice; D016513:Mice, SCID; D009164:Mycobacterium Infections / Q000276:immunology*; D009162:Mycobacterium avium; D012333:RNA, Messenger / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology*
chemical_list: D016207:Cytokines; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma