Heavy and light chain composition of serum IgA and IgA rheumatoid factor in Henoch-Schönlein purpura.
OBJECTIVE
To characterize the heavy and light chain composition of serum IgA and IgA rheumatoid factor (RF) in 34 children with Henoch-Schönlein purpura (HSP).


METHODS
Serum IgA and IgA subclass concentrations were measured by radial immunodiffusion. IgA-RF and the light chain composition of serum IgA and IgA-RF were determined by enzyme immunoassay.


RESULTS
Serum IgA and IgA1 concentrations were higher in HSP patients than controls (P = 0.0001), but there was no difference in IgA2 concentrations between the two groups. IgA-RF was present in 19 of 34 HSP patients; it was composed predominantly of IgA1. The kappa:lambda ratio of serum IgA was virtually identical in patients and controls, but the kappa:lambda ratio of IgA-RF was significantly higher than that of the serum IgA from the 19 IgA-RF seropositive patients (P = 0.0003).


CONCLUSIONS
Serum IgA1 is preferentially increased in children with HSP, but the light chain composition of IgA is not different from that in controls. IgA-RF is common in HSP; it is composed predominantly of IgA1 and it is enriched in kappa light chains.
Saulsbury
F T
FT
Department of Pediatrics, University of Virginia Health Sciences Center, Charlottesville 22908.
D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D011695:IgA Vasculitis / Q000276:immunology*; D007070:Immunoglobulin A / Q000032:analysis / Q000737:chemistry*; D007147:Immunoglobulin Light Chains / Q000032:analysis; D007145:Immunoglobulin kappa-Chains / Q000032:analysis; D008297:Male; D012217:Rheumatoid Factor / Q000032:analysis / Q000737:chemistry*
D007070:Immunoglobulin A; D007147:Immunoglobulin Light Chains; D007145:Immunoglobulin kappa-Chains; D012217:Rheumatoid Factor