Serial Changes in the Galactosylation of Autoantibodies and Serum IgG in Autoimmune Haemolytic Anaemia

Abstract

A number of systemic autoimmune diseases are associated with increased levels of the agalactosyl (G₀) IgG isoforms that lack a terminal galactose from the C_H2 domain oligosaccharide. The aims were to determine whether there are also persistently high levels of G₀ autoantibodies or serum IgG in autoimmune haemolytic anaemia (AIHA), and whether any changes in galactosylation over time are related to the course of disease. Autoantibodies eluted from red blood cells, and serum IgG, were obtained from a patient with chronic AIHA over a 21 month period, and the degree of galactosylation measured using a lectin-binding assay. There were wide fluctuations in the galactosylation of autoantibody and serum IgG, but these changes were unrelated to the severity of the anaemia. The galactosylation of autoantibody and serum IgG varied independently, and the autoantibodies were preferentially G₀ in comparison with serum IgG in only half of the serial samples. We conclude that AIHA differs from other, systemic autoimmune conditions in that high levels of G₀ autoantibodies or serum IgG are not persistent, and that changes in galactosylation do not parallel the course of disease.

Key Words:

• Agalactosyl IgG
• Autoantibody
• Red blood cell
• Autoimmune haemolytic anaemia