There is relatively little literature on the function and regulation of macrophages in the kidney, where they are dismissed as interstitial cells, and sometimes considered fibroblastic rather than macrophage-like. F4/80 antigen is expressed on large numbers of stellate cells in the kidney, as shown in this view of the renal cortex. The cells are commonly associated with the vasculature and spread in the plane of the renal tubules.
The medulla of the kidney contains large numbers of interstitial cells between the tubules. Renal medullary interestial cells are considered a major source of prostaglanding E2 in the kidney, and the regulation of their function contributes to the control of renal blood flow and filtration. F4/80-positive interstitial cells are most numerous in the medulla of the kidney as shown in this view.
Renal medullary interstitial macrophages could be implicated in the control of renal blood flow and filtration. This view of the F4/80-positive macrophages of the renal medulla shows their spreading pattern in longitudinal sections of renal tubules. Note the way they extend processes so that almost every epithelial cell has F4/80-positive macrophage processes associated with the underlying basement membrane. F4/80-positive cell bodies tend to be associated with capillaries, which can seen as small spaces in several parts of the section.
The juxtaglomerular complex contains the afferent and efferent vessels of the major filtration unit of the kidney, the glomerulus. These vessels control the blood flow and rate of filtration by the glomerulus. This view shows the large numbers of F4/80-positive macrophages surrounding these key blood vessels, in a location where they could clearly contribute to regulation of renal function. Note that there are no F4/80-positive cells in the glomerulus itself. The mesangial cells, which may have some phagocytic function, do not express F4/80 or several other macrophage markers.