Cross-reactivity of IgA antibodies between renal mesangial areas and nuclei of tonsillar cells in patients with IgA nephropathy.

A study on autoradiographical analysis of antigenic sites in patients with IgA nephropathy is described. Renal biopsy specimens were obtained from patients with IgA nephropathy. These specimens were treated with citrate buffer (pH 3.2) and the 'eluate' was neutralized by sodium hydroxide. The 'eluate' was labelled with 125iodine by the chloramine-T method. 125I-labelled eluate was then applied to the tonsillar cells obtained from the same and other patients with IgA nephropathy as well as to those with other glomerular diseases. The tonsillar cells were dipped into the emulsion (NBT-2) and then examined with a light microscope. It was demonstrated that the antibodies eluted from renal tissues of patients with IgA nephropathy specificially bound with the nuclear regions of tonsillar cells. The binding of eluted antibodies and tonsillar cells was completely inhibited by the addition of anti-human IgA antisera, but not inhibited by human IgA myeloma proteins. The eluted antibodies bound with tonsillar cells from the same patients, but only 10% of them bound with the tonsillar cells obtained from other patients with IgA nephropathy. It is concluded that IgA antibodies deposited in glomeruli specifically bind with tonsillar cells obtained from patients with IgA nephropathy and these antibodies show some heterogeneity among those patients.