The IgM and IgG subclass distribution of anti-Galactose-alpha-1,3-galactose and anti-N-glycolylneuraminic acid antibodies in healthy adults

Abstract

Abstract Background The major xenoreactive antibodies (Abs), anti-galactose-alpha-1,3-galactose (Gal) and anti-N-glycolylneuraminic acid (Neu5Gc), exist naturally in humans and can contribute to several immunological pathogenesis in xenotransplantation. In this study, we investigated the serum titers of anti-Gal and anti-Neu5Gc Abs including the IgM, IgG, and IgG subclasses in humans to gather basic population data before launching clinical xenotransplantation. Methods Serum titers of anti-Gal and anti-Neu5Gc Abs were measured in 380 healthy adults using an in-house-developed enzyme-linked immunosorbent assay. The detection frequency and distribution of anti-Gal and anti-Neu5Gc IgM, IgG and IgG subclass were evaluated. Results The detection frequencies of Abs were as follows: for anti-Gal, IgG, 95.0%; IgM, 99.2%; IgG1, 23.2%; IgG2, 94.5%; IgG3, 12.4%; and IgG4, 3.4%, and for anti-Neu5Gc, IgG, 96.6%; IgM, 87.4%; IgG1, 1.6%; IgG2, 46.3%. The median titers of anti-Gal IgG (1,198 ng/ml, range <401 – 128,758 ng/ml) and IgM (996 ng/ml, range <113 – 24,698 ng/ml) were significantly higher than those of anti-Neu5Gc Abs (IgG, 194 ng/ml, range <30 – 12,415 ng/ml; IgM, 328 ng/ml, range <154 – 6,514 ng/ml; all P<0.001). IgG2 of both anti-Gal and anti-Neu5G Abs correlated better with the IgG class than other IgG subclasses (rs = 0.762, P < 0.001; rs = 0.606, P < 0.001). Conclusions Most healthy adults possess anti-Gal and anti-Neu5Gc IgG and IgM in their sera. Overall, the titers of anti-Gal Abs are higher than those of anti-Neu5Gc Abs. IgG2 seems to be the main IgG subclass in both anti-Gal and anti-Neu5Gc natural Abs. Changes in the titers of these Abs would be a clue to understand an immunological pathogenesis in the recipients of xenotransplantation.