1,523 publications from this institution
Toll-like receptors (TLRs) are evolutionarily conserved proteins that recognize microbial molecules and initiate host defense. To investigate how TLRs work together to fight infections, we tested the role of TLRs in host defense against the Gram-negative bacterial pathogen, Salmonella. We show that TLR4 is critical for early cytokine production and killing of bacteria by murine macrophages. Interestingly, later on, TLR2, but not TLR4, is required for macrophage responses. Myeloid differentiation factor 88, an adaptor protein directly downstream of TLRs, is required for both early and late responses. TLR4, TLR2, and myeloid differentiation factor 88 are involved in murine host defense against Salmonella in vivo, which correlates with the defects in host defense observed in vitro. We propose a model where the sequential activation of TLRs tailors the immune response to different microbes.
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-gamma (IFN-gamma)-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.
