Diverse myeloid cells are recruited to the developing and inflamed mammary gland

The immune system plays fundamental roles in the mammary gland, shaping developmental processes and controlling inflammation during infection and cancer.Here, we reveal unanticipated heterogeneity in the myeloid cell compartment duringdevelopment of virgin, pregnant, lactating and involuting mouse mammary glands,and in milk. We investigate the functional consequences of individual and compoundchemokine receptor deficiency on cell recruitment. Diverse myeloid cell recruitmentwas also shown in models of sterile inflammation and bacterial infection.Strikingly, we have shown that inflammation and infection can alter the abundanceof terminal end buds, a key developmental structure, within the pubertal mammarygland. This previously unknown effect of inflammatory burden during puberty couldhave important implications for understanding pubertal development.