Effect of CCR2 deficiency in macrophages and T cells on cytokine production or alloreactivity to host antigens. CCR2 deficiency of macrophages and T cells does not impair cytokine production or alloreactivity to host antigens in vitro and in vivo. (A) Naive alveolar macrophages of CCR2^+/+ (▪) or CCR2^-/- (▦) mice were stimulated in vitro for 4 hours with different concentrations of LPS, and TNF-α levels in the supernatant were determined by ELISA. (B) Pulmonary macrophages were harvested 6 weeks after CCR2^+/+ (▪), CCR2^-/- (▦), or syngeneic (□) BMT and stimulated with LPS in vitro; ^*P < .01. (C) (D) (E) Allo-specific proliferation (panel C) and in vitro IFN-γ (panel D) and TNF-α (panel E) production were assessed in a mixed lymphocyte reaction with CCR2^+/+ (▪) or CCR2^-/- (▦) T cells and allogeneic B6D2F₁ stimulators or with CCR2^+/+ (□) T cells and syngeneic B6 stimulators. (F) Cytotoxic function of T cells was determined by an alloantigen-specific cytotoxic T lymphocyte (CTL) assay using P-815 (H2^d) and EL-4 (H2^b) target cells as described (▪, CCR2^+/+ → P-815; •, CCR2^-/- → P-815; ▴, CCR2^+/+ → EL-4; ♦, CCR2^-/- → EL-4). All data presented are from 1 experiment representative of 3. (G) (H) (I) No differences in splenic T-cell expansion, serum IFN-γ, or serum TNF-α levels were observed after allogeneic CCR2^+/+ (▪) or CCR2^-/- (▦) BMT, and measurements in both allogeneic groups were greater than in syngeneic controls (□). Data are presented as mean ± SEM from 1 of 2 comparable experiments; n = 4 to 5 per group; ^*P < .01.