Circulating antibodies to prothymosin alpha in systemic lupus erythematosus.

Autoantibodies to prothymosin alpha, an immunoactive protein that exists in a large variety of mammalian tissues, were found to be present in patients with systemic lupus erythematosus (SLE) by a new, sensitive, and specific anti-prothymosin alpha ELISA. The antigen was prothymosin alpha, purified by high-pressure liquid chromatography from goat spleen extracts. Sera from 44 SLE patients and 276 healthy individuals were screened for the presence of anti-prothymosin alpha activity; 18% of SLE sera were found to be positive, compared with 1.8% of control sera. This anti-prothymosin alpha activity appears to be idiotypically distinct from either anti-thymosin alpha 1 activity or anti-dsDNA activity, as demonstrated by inhibition experiments. Significant positive correlation exists between anti-prothymosin alpha and anti-dsDNA activities of SLE sera (r = +0.596, n = 36, P less than 0.001), while no correlation was observed with the clinical activity (X2 = 1.239, 0.1 less than P less than 0.5) or with complement levels C3 and C4.