title: Anti-immunoglobulin antibodies in children with Schönlein-Henoch syndrome. Absence of serum anti-IgA antibodies.
abstract: Circulating immune complexes (CIC) that simultaneously contain IgG and IgA are frequently found in IgA nephropathy (IgA-N) and the Schönlein-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 level of IgG anti-IgA antibodies (240 +/- 104 u/ml) in SHS patients was similar to control values (251 +/- 85 u/ml); the IgA anti-IgG antibodies were increased, although only the antibodies against Fc fraction of IgG were elevated (185 +/- 71 u/ml in patients vs 127 +/- 24 mu/ml in controls, 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 also high IgA anti-IgGFab. None of these patients had high IgA anti-IgGFab antibodies without simultaneous augmentation of IgA anti-IgGFc. Only 3/39 (7.7%) of SHS patients showed high levels of IgG anti-IgA antibodies. The correlation of IgA anti-IgGFc antibodies with IgA anti-IgGFab was very strong (P < 0.0001) but lower with IgG anti-IgA antibodies (P < 0.002). In addition, 8/39 children had renal involvement, nevertheless in these patients the findings were quite similar, with a non-significant elevation of IgA anti-IgGF ab antibodies. These results show 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 anti-bodies against IgG and not vice versa.
authors.affiliation: Facultad de Medicina, Pediatría, Vallodolid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Blanco Quirós
authors.forename: C
authors.initials: C
authors.lastname: Blanco
authors.forename: J
authors.initials: J
authors.lastname: Alvarez
authors.forename: P
authors.initials: P
authors.lastname: Solis
authors.forename: F
authors.initials: F
authors.lastname: Conde
authors.forename: S
authors.initials: S
authors.lastname: Gomez
mesh_terms: D000888:Antibodies, Anti-Idiotypic / Q000097:blood*; D000936:Antigen-Antibody Complex / Q000097:blood; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D011695:IgA Vasculitis / Q000276:immunology*; D007070:Immunoglobulin A / Q000276:immunology*; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D008297:Male
chemical_list: D000888:Antibodies, Anti-Idiotypic; D000936:Antigen-Antibody Complex; D007070:Immunoglobulin A; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G