Correlative expression of C3b receptors in the glomerulus and on erythrocytes.

The reactivity of glomerular C3b receptors (CR1) measured by the number of sheep erythrocytes bearing C3b (EAC) that adhered to glomeruli in frozen sections, was compared with the reactivity of erythrocyte CR1, which was determined by immune adherence hemagglutination (IAHA), in 22 patients with renal and non-renal diseases. Among seven patients with primary glomerulonephritis whose erythrocytes were positive for IAHA, the reactivity of glomerular CR1 was high in five. In the remaining two, the reactivity of glomerular CR1 was low, accompanied by severe sclerotic glomerular changes. Erythrocytes from five of six patients with systemic lupus erythematosus were IAHA negative, and their glomeruli failed to produce adherence of EAC, even in three cases in which there were no detectable C3 deposits or histopathological changes. In the other nine patients without appreciable glomerular changes, the reactivity of glomerular CR1 was low in three along with negative erythrocyte IAHA, whereas the remaining six exhibited high CR1 reactivity both in glomeruli and on erythrocytes. The results indicate a close correlation between the expression of CR1 in the glomerulus and on erythrocytes.