Regulation of granuloma fibrosis by nitric oxide during Mycobacterium avium experimental infection

Authors

  • Susana Lousada,

    1. Laboratory of Microbiology and Immunology of Infection, IBMC-Institute for Molecular and Cell Biology, University of Porto, Porto, Portugal
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  • Manuela Flórido,

    1. Laboratory of Microbiology and Immunology of Infection, IBMC-Institute for Molecular and Cell Biology, University of Porto, Porto, Portugal
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  • Rui Appelberg

    1. Laboratory of Microbiology and Immunology of Infection, IBMC-Institute for Molecular and Cell Biology, University of Porto, Porto, Portugal
    2. ICBAS-Instituto de Ciências Biomédicas de Abel Salazar, University of Porto, Porto, Portugal
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Rui Appelberg
Laboratory of Microbiology and Immunology of Infection
Institute for Molecular and Cell Biology
Rua do Campo Alegre 823
4150-180 Porto
Portugal
Tel.: +351 22 607 4952
Fax: +351 22 609 9157
E-mail: rappelb@ibmc.up.pt

Summary

Collagen deposition within granulomas formed after Mycobacterium avium infection was analysed on histological sections stained with Masson's trichrome using acquired computerized image analysis and a program that was specifically designed for that purpose. Comparison was made between immunocompetent C57BL/6 mice and mice genetically deficient in the inducible nitric oxide (NO) synthase gene (iNOS–/– mice) infected with either a highly virulent strain or a moderately virulent strain of M. avium. iNOS-deficient mice were more resistant to the highly virulent strain than control C57B1/6 mice, but both strains were equally susceptible to the less virulent M. avium strain. Collagen distribution in the granuloma was found in the cuff surrounding the granuloma in an area rich in lymphoid cells as well as inside the granuloma itself, conferring a mesh-like structure within that lesion. It was seen that iNOS–/– mice induced a higher collagen deposition than C57BL/6 mice and that such collagen deposition varied with the mycobacterial strain used to infect the animals.

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