Localization of an Ia-bearing glomerular cell in the mesangium.

Using trypsin to render intact, isolated rat glomeruli permeable to antibody, and using an electron microscopic immunoperoxidase technique, we have localized a phagocytic immunologically-relevant cell bearing Ia determinants to the renal mesangium. Thus there are at least two functionally distinct cell types in the renal mesangium: one is a contractile smooth musclelike cell, and the other a phagocytic cell that bears immunologically-relevant surface determinants.