Abnormally high humoral responses have been described in IgA nephropat
hy (IgAN), towards antigens commonly involved in infectious events or
food intolerance. Here we report a comparative analysis of humoral res
ponses to a common environmental antigen, dextran B 512, present both
in nonpathogenic microorganisms and normal diet. Dextran-specific IgG,
IgA and IgM were assayed using an ELISA method in serum samples from
121 patients with IgAN, 40 controls and 32 patients with biopsy-proven
renal diseases different from IgAN. Among the latter, 17 were transpl
ant recipients. Anti-dextran IgG antibodies were found significantly (
p < 0.05) more frequently and at higher levels in IgAN patients than i
n patients with other renal diseases. Anti-dextran IgA were at signifi
cantly (p < 0.05) higher levels in IgAN patients than in controls or u
ntransplanted NIgAN patients, However, similarly elevated levels of an
ti-dextran IgA were found in IgAN patients and transplanted patients w
ith other renal diseases. These data confirm that IgA and IgG response
s towards common antigens are elevated in IgAN, possibly as a conseque
nce of the pathogenesis of this disease rather than because of renal i
mpairment. Moreover, since the same degree of dysregulation was noted
in the control group of transplanted patients whose initial diagnosis
was not IgAN, these data favour the hypothesis of a global dysregulati
on of the IgA system in IgAN, yielding enhanced humoral immune respons
es to possible pathogens and diet antigens.