This study was performed to isolate and investigate the
IgA1 that could accumulate in glomeruli (glomerulophilic
IgA1).
IgA1 was fractionated by the electric charge and the reactivity to
Jacalin. Serum
IgA1 of
IgA nephropathy patients was separated and fractionated using a
Jacalin column and subsequent ion-exchange chromatography. The fractions were divided into three groups of relatively cationic (C), neutral (N), and anionic (A).
IgA1 was also divided into
Jacalin low (L), intermediate (I), and high (H) affinity fractions by serial elution using 25, 100, and 800 mM
galactose. The left kidneys of Wistar rats were perfused with 2, 5, or 10 mg of each group of
IgA1. The rats were sacrificed 15 min, 30 min, 3 h, or 24 h after the perfusion. The accumulation of each
IgA1 in the glomeruli was then observed by immunofluorescence. The
IgA1 of the fractions N and H separated by the two methods was definitely accumulated in the rat glomeruli with a similar pattern. The electrophoresis revealed that the macromolecular
IgA1 was increased in fraction H compared with other fractions. Therefore,
Jacalin high-affinity
IgA1(fraction H) was applied on a diethylaminoethyl column and divided into electrically cationic (HC), neutral (HN), and anionic (HA). Only the asialo-Galbeta1,3GalNAc chain was identified in the fraction HN
IgA1 by gas-phase hydrazinolysis. Furthermore, the
IgA1 fraction was strongly recognized by
peanut agglutinin, Vicia Villosa
lectins, and antisynthetic hinge
peptide antibody. These results indicated that the
IgA1 molecules having the underglycosylated hinge
glycopeptide played a certain role in the glomerular accumulation of
IgA1 in
IgA nephropathy.