Limited role of the Toll‐like receptor‐2 in resistance to Mycobacterium avium

Summary The role of the Toll‐like receptor (TLR)‐2 in the generation of protective immunity to Mycobacterium avium was evaluated using gene‐disrupted mice. TLR‐2−/− mice were more susceptible than wild‐type C57Bl/6 mice to M. avium strains that were able to proliferate in vivo before the development of protective immunity and mycobacteriostasis. In contrast, the elimination of non‐virulent strains was not affected by the mutation. The generation of interferon‐γ (IFN‐γ)‐producing T cells and the expression of the interleukin‐12 p40 gene were reduced in TLR‐2‐deficient mice as compared to C57Bl/6 mice early during infection with M. avium strain 2447. The generation of protective CD4+ T cells was also compromised in the mutated mice as compared with the controls. Our data show that TLR‐2 is required for optimal immunity against certain virulent M. avium strains.