Functionally distinct resident macrophage subsets differentially shape responses to infection in the bladder

Abstract

Resident macrophages are abundant in the bladder, playing key roles in immunity to uropathogens. Yet, whether they are heterogeneous, where they come from, and how they respond to infection remain largely unknown. We identified two macrophage subsets in mouse bladders, MacM in the muscle and MacL in the lamina propria, with distinct protein expression and transcriptomes. Using a urinary tract infection model, we validated our transcriptomic analyses, finding that MacM macrophages phagocytosed more bacteria and polarized to a more anti-inflammatory profile, whereas the MacL subset died rapidly during infection. During resolution, monocyte-derived cells contributed to tissue-resident macrophage pools and both subsets acquired transcriptional profiles distinct from naive macrophages. Depletion of these altered macrophages resulted in the induction of a type 1 biased immune response to a second urinary tract infection, improving bacterial clearance. Our study uncovers the biology of resident macrophages and their response to an exceedingly common infection in a largely overlooked organ, the bladder.