Differential contribution of Toll-like receptors 4 and 2 to the cytokine response to Salmonella enterica serovar Typhimurium and Staphylococcus aureus in mice

Abstract

The contribution of murine Toll-like receptors 2 and 4 (TLR2 and -4, respectively) to cytokine induction by heat-killed bacteria was analyzed in vitro and in vivo. Gram-negative bacteria induced cytokines primarily via TLR4; the contribution of TLR2 was only minor. Neither TLR4 nor, surprisingly, TLR2 was required in the MyD88-dependent response to Staphylococcus aureus.

FIG. 1.

Role of TLR4 and TLR2 in the IL-6 response of macrophages to LPS or synthetic LP (Pam3CysSK4). Bone marrow-derived macrophages of wild-type, TLR4-deficient, TLR2-deficient, and TLR2/TLR4 double-deficient mice were stimulated with different amounts of LPS (left panels) or LP (right panels) for 4 h (TNF-α) and 24 h (IL-6). IL-6 (a) and TNF-α (b) were measured in cell supernatants. One representative experiment of 10 is shown.

FIG. 2.

Role of TLR4 and TLR2 in the IL-6 and TNF-α responses of macrophages to heat-killed S. enterica serovar Typhimurium and S. aureus. Bone marrow-derived macrophages of wild-type, TLR4-deficient, TLR2-deficient, and TLR2/TLR4 double-deficient mice were stimulated with different amounts of heat-killed S. enterica serovar Typhimurium (left panels) or S. aureus (right panels) for 4 h (TNF-α) and 24 h (IL-6). IL-6 (a) and TNF-α (b) were measured in cell supernatants. One representative experiment of 10 is shown.

FIG. 3.

Role of MyD88 in the IL-6 and TNF-α responses of macrophages to heat-killed S. aureus. Bone marrow-derived macrophages of wild-type (C57BL/6) and MyD88-deficient mice were stimulated with different amounts of heat-killed S. aureus for 4 h (TNF-α) and 24 h (IL-6). IL-6 and TNF-α were measured in cell supernatants. One representative experiment of two is shown.

FIG. 4.

Roles of TLR4 and TLR2 in the TNF-α and IL-6 responses to S. enterica serovar Typhimurium in unprimed and P. acnes-primed mice. Wild-type, TLR4-deficient (def.), TLR2-deficient, and TLR2/TLR4 double-deficient mice (6 to 9 animals per group) were injected intravenously with P. acnes (25 μg/g of body weight) or remained untreated (control). Seven days later, all mice were challenged with different amounts of S. enterica serovar Typhimurium. Plasma was collected 1 h (TNF-α) and 2 h (IL-6) after challenge.

FIG. 5.

Role of TLR4 and TLR2 in the TNF-α and IL-6 response to S. aureus in unprimed and P. acnes-primed mice. Wild-type, TLR4-deficient, TLR2-deficient, and TLR2/TLR4 double-deficient mice (6 to 9 animals per group) were injected intravenously with P. acnes (25 μg/g of body weight) or remained untreated (control). Seven days later, all mice were challenged with S. aureus (15 μg/g of body weight). Plasma was collected 1 h (TNF-α) and 2 h (IL-6) after challenge.