Nlrp1bS/SCasp1−/− mice which harbored LT-resistant macrophages and did not activate and release IL-1β in response to LT injection were fully susceptible to infection when compared to Nlrp1bS/S Casp1+/− and Nlrp1bS/S Casp1+/+ littermates, confirming that caspase-1 was required for Nlrp1bS-mediated resistance to anthrax infection. This evidence concerns the gene IL1B and infection.