TLR2 and infection: Similar to the infection studies, there was negligible secretion of proinflammatory cytokines by ΔTLR2 and ΔMyd88 cells, confirming that PE18 and PPE26 elicit production of proinflammatory cytokines by murine macrophages mediated by the innate immune receptor TLR2 and adapter Myd88 (Figures 4D–F).