We suspect that it may play an important role, because broad depletion of macrophages using clodronate liposome injection at 7 weeks of infection caused a significantly more rapid onset of lethal disease than did DT administration to CCR2-DTR mice, such that all treated animals (n = 15) died within 24 h (data not shown; clodronate treatment of naïve mice caused no noticeable ill effects). This evidence concerns the gene CCR2 and infection.