CD137L+Macrophage Resolves Acute Cystitis Induced by UPEC Infection through Regulatory T Cells Activation

Urinary tract infections (UTIs) typically evoke prompt and vigorous innate immune responses in bladder, but the specific mechanisms that resolute acute inflammation remain unclear. In this study, single-cell RNA sequencing and analysis of immune cells from the bladder at early stage of uropathogenic Escherichia coli (UPEC) infection was performed. The increased hyperactivated CD137L+macrophage response and decreased immunosuppressive Treg cells are elucidated in the bladder microenvironment of UPEC infection. Conditional depletion of CD137L in macrophage aggravates inflammatory reaction, bacterial load and urothelium destruction. Deletion of Treg cells also aggravated inflammation while promoting urothelial injury after UPEC infection. Additionally, Treg cells were increased in infected bladder which can be reversed by a myeloid-CD137L deletion. We thought activation of Treg cells by CD137L+macrophage is a key mechanism for suppressing acute inflammatory reaction after UPEC infection. The present study provided new insights into the functions of myeloid-CD137L dependent Treg cells in the immune response to UPEC infection.