ABNORMAL IGA GLYCOSYLATION IN HENOCH-SCHONLEIN PURPURA RESTRICTED TO PATIENTS WITH CLINICAL NEPHRITIS

Background. Glomerular deposition of IgA1 is a common feature of Henoc h-Schonlein purpura, and is indistinguishable from that seen in IgA. n ephropathy. Serum IgA1 is abnormally O-glycosylated in IgA nephropathy , and this may contribute to mesangial IgA1 deposition and the develop ment of glomerular injury. This altered O-glycosylation of IgA1 can be detected by its increased binding to the lectin Vicia villosa. Method s. To investigate whether IgA1 is abnormally glycosylated in Henoch-Sc honlein purpura, the binding of Vicia villosa lectin to serum IgA1 was studied in the following subject groups: IgA nephropathy; adults and children with Henoch-Schonlein purpura and nephritis; children with cl inically diagnosed Henoch-Schonlein purpura but no renal involvement; adults and children with non-IgA associated glomerulonephritis; and ma tched controls. Results. The abnormality of lectin binding seen in IgA nephropathy was also found in both adults and children with Henoch-Sc honlein purpura with nephritis. However, the lectin binding of serum I gA1 from children with Henoch-Schonlein purpura lacking renal involvem ent did not differ from controls, and similarly, no abnormality of lec tin binding was seen in patients with non-IgA associated glomeruloneph ritis. Conclusions. These data indicate that the abnormality of IgA1 O -glycosylation seen in IgA nephropathy is also found in Henoch-Schonle in purpura, but only in those subjects with renal involvement, while I gA1 O-glycosylation is normal in patients with other forms of renal di sease. These findings lend strong support to a role for altered IgA1 O -glycosylation in the pathogenesis of IgA-associated glomerular diseas e.