Here we demonstrate that CCR2 expression is significantly elevated during Chlamydia muridarum (C. muridarum) respiratory infection, and its absence leads to exacerbated susceptibility, as evidenced by significant weight loss, higher bacterial loads, severe lung pathology, and elevated levels of inflammatory cytokines (il-1β, tnfα, and il-6). This evidence concerns the gene TNF and respiratory tract infectious disorder.