IL17A and chlamydia trachomatis infectious disease: IL‐22 has been suggested to cooperate with IL‐17 in the host defence against chlamydial infection 38, so we examined the change in IL‐22 production after NK‐cell depletion and found that the level of IL‐22 was significantly lower in NK cell–depleted mice than control mice by splenocytes, lung mononuclear cells, mediastinal lymph node cells and serum (Fig. 3D–G).