Based on the results of the transcriptome analysis, we speculate that IL-21 may affect the inflammation level after chlamydia infection by regulating macrophage polarization, so we firstly explore the M1/M2 balance in the lungs of WT mice and IL-21R−/− mice on days 0, 3, 7, and 14 p.i. by flow cytometry. The gene discussed is IL21; the disease is chlamydia infectious disease.