IL17A and infection: The etiology of BPD is considered to include lung immaturity, infection and inflammation, mechanical ventilation, oxygen poisoning, etc. In the development of BPD, inflammation is an essential regulatory factor [2], while type 3 innate lymphoid cells (ILC3) have been found to play a proinflammatory role in inflammatory intestinal diseases through secreting cytokines interleukin-17 (IL-17) and interleukin-22 (IL-22) [5].