Recombinant interleukin-6 increases the intracellular and extracellular growth of Mycobacterium avium |
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Authors: | M Denis E O Gregg |
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Institution: | ICI Pharmaceuticals, Macclesfield, Cheshire, England. |
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Abstract: | Human monocytes were isolated from the peripheral blood of normal donors and allowed to differentiate in vitro into macrophages. The susceptibility of these cells to infection with a virulent Mycobacterium avium and its modulation by some soluble factors was monitored. The virulent strain of Mycobacterium avium grew progressively in untreated macrophage monolayers. Interleukin-6 (IL-6) was tested for its ability to modulate the macrophage-mycobacteria interaction. Surprisingly, IL-6 was shown to increase M. avium growth in macrophage monolayers by twofold as compared with untreated cells, when added before or after infection. Moreover, addition of rIL-6 to replicating mycobacteria in vitro enhanced their growth two- to three-fold as compared with cultures treated with rIL-6 and a rabbit antiserum to rIL-6. Treatment with IL-6 and interferon-gamma (IFN-gamma) or IL-4 did not modify the growth promoting effect of IL-6 in human macrophages. Overall, our results suggest that IL-6 may contribute significantly to the pathogenesis of infections with M. avium by promoting mycobacterial growth. |
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