Immunofluorescence and ultrastructural localization of beta 2-microglobulin in human renal allografts

The localization of beta 2-microglobulin (beta 2m) was studied in renal biopsies from 18 patients with pathological transplanted kidney using immunofluorescence and electron-immunohistochemical techniques; the renal biopsies of 4 cases with normal kidneys were used as controls. Using immunofluorescence, beta 2m was not observed in the normal kidneys, beta 2m was found in the glomeruli (7 cases) and the tubular epithelium (16 cases) of the transplanted kidneys. Using immunoelectron microscopy, some labelling of the normal kidneys was observed mainly along the cell coat of foot processes and in tubular-epithelial lysosomes. In the glomeruli of transplanted kidneys, particularly in cases of acute or chronic rejection, beta 2m was most frequently localized on the outer layer of the basement membrane and along the cell coat of foot processes. The brush border of the proximal tubules and the lysosomal structures were intensely labelled. Although immunoelectron-microscopy studies are unable to discriminate between the localization of beta 2m in normal and transplanted kidneys, these findings nevertheless suggest the glomerular filtration of beta 2m and its metabolism in the tubular epithelium.