Renal allografts in cystinosis and mesangial demography.

Twenty-four biopsies of generally cadaveric renal allografts from 20 patients with cystinosis were examined by light, polarization, phase contrast and electron microscopy. Cystine crystals, or cytoplasmic crystalline spaces compatible with cystine, were observed in interstitial cells in 23 of the 24 biopsies and in glomeruli in six. Among the six, crystalline spaces were identified by electron microscopy in cells compatible with macrophages in the mesangium in two, and, in one of the latter, dark, presumably cystine-containing cells were also present in the mesangium. On the premise that cystine-containing cells derive from the host, these findings support the thesis that in man cells of the mononuclear phagocyte system of extrarenal origin may exist in the mesangium. However, in comparison with infiltration of the interstitium, infiltration of the glomerulus by macrophages from extrarenal sources is scant, as studied under conditions of renal transplantation.