IGA NEPHROPATHY - CHARACTERIZATION OF THE POLYMERIC NATURE OF MESANGIAL DEPOSITS BY INVITRO BINDING OF FREE SECRETORY COMPONENT

Abstract

IgA nephropathy, as Berger defined it, is characterized by mesangial deposits of IgA, which are easily visualized by immunofluorescence on [human] kidney biopsies. The structure (mono- or dimeric) of these IgA has not been clearly defined so far. Fifteen renal biopsies were studied to find out whether these IgA are serum monomers, or are polymers from a different origin. This was done by tissue fixation in vitro of free secretory component, which was then visualized by immunofluorescence (IF). In all 15 cases, the IgA deposits lacked bound secretory component, but were able to bind, specifically, with the free secretory component. The presence of J chain in these deposits was also evidenced by indirect IF. These findings favor the hypothesis that these Ig are polymeric.