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 ery thematosus (SLE) is influenced by genetic factors. The presence of autoanti bodies in healthy family members of patients has been reported. Our hypothe sis 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 fir st-degree family members, and 330 healthy controls. Presence of autoantibod ies 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 membe rs, and 1.5% of healthy controls had antibodies against any nuclear antigen . Most frequent autoantibodies in the patients were anti-histone and anti-S SA, whereas in the family members these were anti-RNP-C and anti-Topo-I/Scl . Presence and specificity of autoantibodies in family members were indepen dent of the presence or absence of that autoantibody in their patient relat ive (chi-square p > 0.1 for all 14 antigens). Conclusion. Autoantibodies in family members and their patient relatives ar e not directed against the same nuclear antigens. Thus a familial aspecific dysfunction of the B lymphocyte is the most likely explanation for autoant ibody production in SLE.