Anthrax produces at least two toxins that cause an intense systemic inflammatory response, edema, shock, and eventually death. The relative contributions of various elements of the immune response to mortality and course of disease progression are poorly understood. We hypothesized that knockout mice missing components of the immune system will have an altered response to infection. Parent strain mice and knockouts were challenged with LD95 of anthrax spores (5 X 10(6)) administered subcutaneously. Our results show that all genetic knockouts succumbed to anthrax infection at the same frequency as the parent. TNF antibody delayed death but TNF receptor 1 knockout had no effect. IL-1 receptor or iNOS knockouts died sooner. Anthrax was more abundant in the injection site of TNF-alpha and iNOS knockouts compared to parent suggesting that attenuated cellular response increases rate of disease progression. With the exception of edema and necrosis at the injection site pathological changes in internal organs were not observed. (C) 2002 Elsevier Science (USA).