CX₃CR1⁺ interstitial dendritic cells form a contiguous network throughout the entire kidney

Dendritic cells (DCs) interface innate and adaptive immunity in nonlymphoid organs; however, the exact distribution and types of DC within the kidney are not known. We utilized CX₃CR1^GFP/+ mice to characterize the anatomy and phenotype of tissue-resident CX₃CR1⁺ DCs within normal kidney. Laser-scanning confocal microscopy revealed an extensive, contiguous network of stellate-shaped CX₃CR1⁺ DCs throughout the interstitial and mesangial spaces of the entire kidney. Intravital microscopy of the superficial cortex showed stationary interstitial CX₃CR1⁺ DCs that continually probe the surrounding tissue environment through dendrite extensions. Flow cytometry of renal CX ₃CR1⁺ DCs showed significant coexpression of CD11c and F4/80, high major histocompatibility complex class II and FcR expression, and immature costimulatory but competent phagocytic ability indicative of tissue-resident, immature DCs ready to respond to environment cues. Thus, within the renal parenchyma, there exists little immunological privilege from the surveillance provided by renal CX₃CR1⁺ DCs, a major constituent of the heterogeneous mononuclear phagocyte system populating normal kidney.