Sialylation of anti-histone antibodies in blood serum of systemic lupus erythematosus patients

Anti-histone autoantibodies belong to main marker antibodies used in the diagnostics of systemic lupus erythematosus (SLE) patients. During autoimmune diseases, especially in SLE, prevalent process of inflammation is caused by high titers of auto-antibodies. It is known that the level of IgG sialylation affect their anti-inflammatory properties. The aim of the experiments was to investigate the level of sialylation of anti-histone IgG-antibodies from blood serum of patients with SLE. Investigation was carried out by two methodological approaches. In the first case, the antibodies were purified from blood serum by affine chromatography on histone-Sepharose and protein G-Sepharose followed by Western blot detection of sialic acid residues in the carbohydrate chaines of IgG molecules using sialospecific previously biotinylated Sambucus nigra lectin (SNA). In the second case, IgG-antibodies were isolated from blood serum by affine chromato­graphy on protein G-Sepharose, this fraction was separated on sialylated and not sialy­lated IgG by SNA-Sepharose chromatography followed by checking their affinity to histones by ELISA. In this manuscript, it is shown that the level of sialylation of anti-histone IgG is lower than in control preparation of antibodies. Our data showed that anti-histone autoantibodies are devoid of sialic acid residues at the ends of the carbohydrate chains of Fc-fragments promote their inflammatory properties in patients with SLE.