Figure 7

Alterations in TNF and IL-10 production do not explain relative resistance of Cd36 ^-/- mice to mycobacterial infection. A. Serum levels of TNF in Cd36 ^+/+ and Cd36 ^-/- mice rose after intraperitoneal infection (day 0) with M. bovis BCG, reaching a maximum after 14-21 days, then decreased. This trend paralleled the mycobacterial counts in organs of infected mice. TNF levels were higher overall (p < 0.001) in Cd36 ^+/+ mice (solid line) compared to Cd36 ^-/- mice (dashed line). Results are displayed as mean ± SEM, with each point representing 4 replicate mice. Data from one representative experiment of two are shown. B. Significant correlation (ρ = 0.596, p < 0.001) between splenic mycobacterial counts and serum level of TNF. C. Time course of TNF production by Cd36 ^+/+ and Cd36 ^-/- thioglycolate-elicited peritoneal macrophages co-incubated with M. marinum in vitro shows no difference between genotypes (p = 0.33). In contrast, TNF production by Tlr2 ^-/- (p < 0.0001) and Irak4 ^-/- (p < 0.0001) macrophages is markedly deficient. D. Cd36 ^-/- macrophages are not deficient in IL-10 production, and produce higher levels of IL-10 at some time points (* p = 0.040) following infection with M. marinum. E and F. TNF production in response to M. marinum (E) and BCG (F) is similar (p = 0.54 for M. marinum, p = 0.96 for BCG) between Cd36 ^+/+ and Cd36 ^-/- macrophages over a range of multiplicities of infection. G and H. IL-10 production in response to M. marinum (G) and BCG (H) was dose-dependent (p < 0.0001 for both) and was higher in Cd36 ^-/- macrophages (p < 0.0001 for M. marinum, p = 0.0003 for BCG). Cytokine levels were assayed in supernatant of macrophages in 96-well plates (200,000 adherent cells and 250 μl media per well) after 24 hours incubation. These findings were confirmed using bone-marrow derived macrophages (data not shown).