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Autoantibodies within families of patients with systemic lupus erythematosus are not directed against the same nuclear antigens.

OBJECTIVE
The presence of antinuclear autoantibodies in systemic lupus erythematosus (SLE) is influenced by genetic factors. The presence of autoantibodies in healthy family members of patients has been reported. Our hypothesis was that autoantibodies are directed against the same antigens in first-degree family members of patients with SLE as in their patient relative.


METHODS
Plasma was harvested from 50 patients with SLE, 154 unaffected first-degree family members, and 330 healthy controls. Presence of autoantibodies against 14 specific nuclear antigens was tested by the ELISA based line immunoassay INNO-LIA method.


RESULTS
Seventy-four percent of patients, 32% of first-degree family members, and 1.5% of healthy controls had antibodies against any nuclear antigen. Most frequent autoantibodies in the patients were anti-histone and anti-SSA, whereas in the family members these were anti-RNP-C and anti-Topo-I/Scl. Presence and specificity of autoantibodies in family members were independent of the presence or absence of that autoantibody in their patient relative (chi-square p > 0.1 for all 14 antigens).


CONCLUSION
Autoantibodies in family members and their patient relatives are not directed against the same nuclear antigens. Thus a familial aspecific dysfunction of the B lymphocyte is the most likely explanation for autoantibody production in SLE.