Anti-alpha-galactosyl antibodies and immune complexes in children with Henoch-Schonlein purpura or IgA nephropathy

Episodes of hematuria in IgA nephropathy or Henoch-Schonlein purpura are
frequently associated with microbial infections. Some of those infectious agents
bear alpha-galactosyl residues on their cell surface. These observations prompted
us to determine, by passive hemagglutination, the titers of natural
anti-galactosyl antibodies in the serum of children presenting with
Henoch-Schonlein purpura (10 cases) or IgA nephropathy (7 cases). Antibody titers
of normal subjects (103 cases), children with a pharyngitis of unknown etiology
(7 cases), and children exhibiting mesangial IgA deposits but no hematuria at the
time of testing (6 cases) ranged from 1:20 to 1:80. Elevated titers (greater than
1:80) were observed in nine of 11 patients with mesangial IgA deposits and micro-
or macroscopic hematuria, in nine of 19 children with other evolutive glomerular
diseases (5 cases of acute glomerulonephritis and 4 cases of minimal change
disease), and in most subjects presenting with a M. pneumoniae (4/5 cases) or a
E. Coli (4/5 cases) infection. Antibody titers decreased after incubation of
normal and pathological sera with D-galactose (10 mM) or with
alpha-galactosyl-glucoside (10 mM), but not with D-glucose (10 mM). The
anti-alpha-galactosyl antibodies purified, by affinity chromatography, from sera
of 10 normal children, 10 pathological controls and four children with mesangial
IgA deposits without hematuria belonged to IgG class. In contrast, both IgG and
IgA anti-alpha-galactosyl antibodies were detected in six of six patients with
mesangial IgA deposits and hematuria. The IgA content of immune complexes
detected in those patients decreased after incubation of sera with
alpha-galactosyl-glucoside, but not with D-glucose.