Induction of granulomas in interferon-  gene-disrupted mice by avirulent but not by virulent strains of Mycobacterium tuberculosis

Abstract

To gain a better understanding of the pathological role of interferon-y (IFN-y) in specific granuloma formation, IFN-y gene-deficient mice (BALB/c and C57BL/6) were produced. The IFN-y gene in embryonic stem (ES) cells was disrupted by inserting the P-galactosidase gene (IacZ) and the neomycin resistance gene ( m u ) at the translation initiation site in exon 1 by homologous recombination. Six-week-old IFN-y-deficient and wild-type mice were inoculated with lo3 -10' bacilli of various strains of Mycobacteriurn tuberculosis (Kurono, H37Rv, H37Ra and BCG Pasteur) through their tail veins. The mice were examined 7 weeks later for granuloma formation. The avirulent BCG Pasteur and H37Ra strains (lo3-lo4 bacilli/ml) induced granulomas in the spleen, liver and lungs of IFN-y-deficient mice. The granulomas consisted of epithelioid macrophages and Langhans multinucleate giant cells, but lacked caseous necrosis. The virulent Kurono and H37Rv strains induced disseminated abscesses but not granulomas in various organs of IFN-y-deficient mice and Mac-3-positive macrophages were not detected in the abscess lesions. These results suggest that IFN-y may be primarily responsible for macrophage activation and that other factor(s) may be involved in the granuloma formation mechanism.

Protective Role of Interleukin-1 in Mycobacterial Infection in IL-1 α/β Double-Knockout Mice

“…Necrotic lesions are induced to a marked extent in IFN-␥, TNF-␣, and IL-12 KO mice (Cooper et al, 1993;Flynn et al, 1993;Kaneko et al, 1999;Sugawara et al, 1998). However, necrotic lesions were not induced in our IL-1 ␣/␤ double KO mice.…”

“…IFN-␥ may be involved in macrophage fusion and the recruitment of epithelioid macrophages to form multinucleated giant cells (Sugawara et al, 1998). Because no multinucleated giant cells were found in our IL-1 KO mice, this effect may be specific to IFN-␥.…”

“…Multinucleated giant cells have been recognized in granulomas of IFN-␥ KO mice, but not in TNF-␣ or IL-18 KO mice (Bean et al, 1999;Kaneko et al, 1999;Sugawara et al, 1998;. IFN-␥ may be involved in macrophage fusion and the recruitment of epithelioid macrophages to form multinucleated giant cells (Sugawara et al, 1998).…”

“…We have previously found that granulomas are induced in mice with a disrupted interferon (IFN)-␥ gene by avirulent forms of Mycobacterium, but not by virulent strains of M. tuberculosis (Sugawara et al, 1998). IFN-␥ may be primarily responsible for macrophage activation in murine experimental tuberculosis (Cooper et al, 1993;Dalton et al, 1993;Flynn et al, 1993;Sugawara et al, 1998). Using tumor necrosis factor (TNF-␣) geneknockout mice, we and other researchers have also shown that TNF-␣ plays an important role in protective immunity against virulent mycobacteria (Bean et al, 1999;Kaneko et al, 1999).…”

Avaliação da virulência micobacteriana e modulação da resposta imune durante a infecção por isolados clínicos de Mycobacterium bovis e Mycobacterium tuberculosis.

“…A indução da fase crônica da infecção observada em camundongos infectados pelo isolado clínico B2, que apresentou virulência intermediária, coincidiu com a indução da produção de IFN- e IL-17 por células obtidas dos pulmões dos camundongos aos 28 dias de infecção. A produção destas citocinas em camundongos C57BL/6 infectados com M. tuberculosis e M. bovis BCG parece refletir no estabelecimento da resposta anti-micobacteriana, sendo estes mediadores importantes para a indução da formação dos granulomas (Cooper et al, 1993;Sugawara et al, 1998;Umemura et al, 2007;Okamoto Yoshida et al, 2010). Após indução da produção das citocinas IFN- e IL-17, nos camundongos infectados com o isolado clínico B2, foi observado queda nos níveis desses mediadores aos 60 dias de infecção (dados não mostrados), porém a carga bacteriana nos pulmões não apresentou aumento.…”