Glomerular findings in mixed IgG-IgM cryoglobulinemia. Light, electron microscopic, immunofluorescence and histochemical correlations.

A case of immune-complex glomerulonephritis with membrano-proliferative patterns in a patient with mixed IgG-IgM cryoglobulinemia has been investigated; particular attention has been payed to histological immunofluorescence, histochemical and electron microscopical findings in order to elucidate the nature of the intraluminal thrombi. The so called thrombi, strongly positive for IgG and IgM with the immunofluorescence, appeared to be clusters of mononuclear cells which, for their ultrastructural and histochemical (non-specific esterase activity) patterns have been considered as monocytes. They showed cytoplasmic vacuoles containing microtubular structures; the latter have been detected free in the capillary lumina and in the basement membranes as well. These structures have been considered as the ultrastructural counterpart of the IgG-IgM immune-complexes responsible of the nephropathy. Monocytes have been hypothesized to play a pathogenetical role, acting as cleaners of the cryoprecipitate from the capillary lumina.