An ultrastructural study of the renal juxtaglomerular apparatus and extraglomerular mesangium in patients with systemic lupus erythematosus.

Experimental studies have indicated that the glomerular mesangium may function by phagocytosis of various circulating substances which are then processed and flow to the juxtaglomerular apparatus (JGA) region and into the intercellular spaces of the macula densa. An electron-micrographic study of the juxtaglomerular apparatus and extramesangial region in systemic lupus erythematosus (SLE) was undertaken. In only five of 39 cases (13%) of SLE were discrete electron-dense "immune-type" deposits noted in the JGA region. In four of those patients, there were also a large number of variously-sized electron-dense deposits in the glomerular mesangial and capillary wall regions, Bowman's capsule, tubular basement membranes, renal interstitium, or in the nearby periglomerular arterioles. The paucity of demonstrable discrete electron-dense deposits in the JGA regions in this study suggests that the deposits noted in SLE in humans may not be commonly processed in this fashion, or alternatively, that the discrete electron-dense deposits are processed and undergo lysis within the glomerular mesangial regions before they are transported to the extraglomerular mesangial regions of the JGA.