Abstract
Increased 16 α-hydroxyestrone (16 α-OHE1) and autoantibodies against histone H1 (H1) have been well described in systemic lupus erythematosus (SLE), but the combination effects of 16 α-OHE1 and H1 remains unclear. Here, we tried to assess the affinity and binding specificity of SLE autoantibodies against the 16 α-OHE1-H1 adduct. IgG was induced against this adduct and was also used as immunochemical probe for the estimation of 16 α-OHE1 in the serum of SLE patients.
The affinity and binding specificities of SLE autoantibodies against 16 α-OHE1-H1 were determined by direct binding and inhibition ELISA as well as quantitative precipitation titration in 60 patients and 30 control subjects.
Purified SLE autoantibodies showed greater recognition to 16 α-OHE1-H1 over H1 (p < 0.05) or 16 α-OHE1 (p < 0.001). The relative affinity of SLE autoantibodies for 16 α-OHE1-H1, H1 and 16 α-OHE1 was 1.41 × 10−7, 1.31 × 10−6, and 1.03 × 10−6, respectively. The concentration of 16 α-OHE1 in the sera of SLE patients was significantly higher than controls (p < 0.05) as estimated by anti-16 α-OHE1-H1 antibodies.
High affinity of 16 α-OHE1-H1 with SLE autoantibodies might suggest an antigenic role of this adduct in the production of these autoantibodies. The anti-16 α-OHE1-H1 antibody is a good immunochemical probe to measure 16 α-OHE1 in different SLE sera.