Antibodies specific for different regions of the IgA1 molecule were used to evaluate tissue from patients with systemic lupus erythematosus (SLE), IgA nephropathy (IgAN), idiopathic membranous nephropathy (IMN), and anti-glomerular basement membrane (GBM) nephritis. One of the IgA1 epitopes was 'masked' in subepithelial and linear BM deposits but was detected in mesangial/subendothelial deposits. This epitope was also hidden following binding of IgA1 antinuclear antibodies (ANA) to nuclear substrates, in vitro. The presence of IgA1 in all loci was confirmed by reactivity of two other monoclonal anti-IgA1 antibodies.
Bibliographical noteFunding Information:
This work was supported in part by grants from the National Institutes of Health (AM07087, A110704, AM22518), the Viking Children's Fund, and the American Heart Association, Minnesota Affiliate. The authors thank Ms. K. Divine, Ms. C. Blocher, and Ms. K. Pinkham for technical assistance; Mr. M. Hoff for the preparation of figures; and Ms. C. Dawis for typing the manuscript.