T cell-dependent inducible nitric oxide synthase production and ultrastructural morphology in BALB/c mice infected with Mycobacterium avium subspecies paratuberculosis

Euthymic BALB/c and athymic nude BALB/c mice aged 3-8 days were infected in traperitoneally with Mycobacterium avium subspecies paratuberculosis (ATCC strain 19698). After euthanasia at 5 months postinoculation, hepatic granul omas were evaluated by morphometric analysis of digital images captured fro m light microscopy sections, by electron microscopy and by immunohistochemi cal methods. Euthymic. mice differed from athymic mice in that (1) their he patic granulomas were smaller, contained fewer bacteria, and produced more inducible nitric oxide synthase, and (2) their hepatic macrophages containe d fewer bacteria, a higher percentage of degraded bacteria, and increased n umbers of primary lysosomes. The study showed that macrophage activation wa s markedly less in the T cell-deficient athymic mice than in the euthymic m ice. (C) 2001 Harcourt Publishers Ltd.