ANTIIMMUNOGLOBULIN ANTIBODIES IN CHILDREN WITH SCHONLEIN-HENOCH SYNDROME - ABSENCE OF SERUM ANTI-IGA ANTIBODIES

Circulating immune complexes (CIC) that simultaneously contain IgG and IgA are frequently found in IgA nephropathy (IgA-N) and the Schonlein -Henoch syndrome (SHS). The presence of anti-immunoglobulin antibodies (IgA anti-IgG and IgG anti-IgA) was studied by ELISA in the serum of 39 children with SHS and compared to 30 normal children. The mean leve l of IgG anti-IgA antibodies (240 +/- 104 u/ml) in SHS patients was si milar to control values (251 +/- 85 u/ml); the IgA anti-IgG antibodies were increased, although only the antibodies against Pc fraction of I gG were elevated (185 +/- 71 u/ml in patients vs 127 +/- 24 mu/ml in c ontrols, P < 0.0001) without a significant increase of IgA anti-IgGFab antibodies (141 +/- 54 mu/ml vs. 137 +/- 25 u/ml); 16/39 (41%) of the patients had increased levels of IgA anti-IgGFc and 6 of these had al so high IgA anti-IgGFab. None of these patients had high IgA anti-IgGF ab antibodies without simultaneous augmentation of IgA anti-IgGFc. Onl y 3/39 (7.7%) of SHS patients showed high levels of IgG anti-IgA antib odies. The correlation of IgA anti-IgGFc antibodies with IgA anti-IgGF ab was very strong (P < 0.0001) but lower with IgG anti-IgA antibodies (P < 0.002). In addition, 8/39 children had renal involvement, nevert heless in these patients the findings were quite similar, with a non-s ignificant elevation of IgA anti-IgGF ab antibodies. These results sho w that the IgA anti-IgG antibodies are more frequently increased than IgG anti-IgA antibodies in the SHS; moreover they are mainly directed against Fc fraction and are IgA-FR isotype. Our findings suggest that the CIC in SHS are likely formed by the reaction of IgA antibodies aga inst IgG and not vice versa.