A single-cell atlas of intestinal immune cells across the day-night cycle reveals dynamic populations.

The small intestine houses an array of immune cells that receive diverse inputs from food intake, microbiota, and other cues that vary by time of day. However, how diurnal variation influences intestinal immune cell proportions and functions is unclear. Here, we use flow cytometry and single cell RNA sequencing to establish an atlas of 815,073 mouse small intestine immune cells at four times across the day-night cycle. These data suggest possible temporal coordination of dendritic cell antigen processing and subsequent T cell antigen recognition. Most cells express circadian clock genes and have intrinsic oscillatory transcriptomes. However, differentiated antibody-producing plasma cells have minimal circadian gene expression and instead may receive extrinsic oscillatory cues from other cell types. Finally, certain populations of B cells are extremely dynamic, with broad transcriptional changes within a six hour time span. This dataset provides insight into the circadian dynamics of intestinal immunity.