Galactosylation of serum IgG and autoantibodies in murine models of 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 CH2 domain oligosaccharide. The current aim was to determine whether the galactosylation of serum IgG is also reduced in a classic antibody-mediated, organ-specific autoimmune condition, and whether the pathogenic autoantibodies are preferentially G0. In two murine forms of autoimmune haemolytic anaemia (AIHA), sera and autoantibodies eluted from erythrocytes were obtained, and the levels of G0 measured using a lectin-binding assay. Serum IgG galactosylation was unaffected following the induction of AIHA in CBA/Igb mice by immunization with rat erythrocytes, but in all animals with the disease the IgG autoantibodies generated were more G0 than the sera. The anti-rat erythrocyte antibodies were similar to the autoantibodies in being preferentially G0, and when CBA/Igb mice were immunized with canine erythrocytes as a control foreign antigen, there was again a bias towards the production of G0 IgG antibodies. In NZB mice with chronic, spontaneous AIHA, the concentration and galactosylation of both serum IgG and autoantibodies were lower than in the induced model, and the ratio of G0 IgG in the serum and erythrocyte eluates varied markedly between different individuals. Our interpretation of these results is that changes in serum IgG or autoantibody galactosylation are not consistent in different models of AIHA, and that production of low galactosyl antibodies can be a feature of a normal immune response.

Production of the effector cytokine interleukin-17, rather than interferon- , is more strongly associated with autoimmune hemolytic anemia

“…4,[34][35][36]38,45 It was, therefore, noteworthy that the levels of a particular Th cytokine, IL-17A, and its production by autoreactive T cells, were not only associated with AIHA but correlated significantly with the severity of the disease. There are precedents for factors related to the T-cell response, which could be considered upstream of the production and hemolytic effects of antibodies, influencing the degree of anemia.…”

“…It can be seen from Figure 1 that, while there is a non-significant (P=0.17; Mann-Whitney U test) trend for higher levels of IFN-γ in the sera of patients than in healthy donors, elevated IL-17A concentrations are very strongly associated with the disease (P<0.001). Many factors determine the severity of anemia in AIHA, 4,[34][35][36] but it was also asked whether the levels of either cytokine in the serum of patients were related to their blood hemoglobin levels. Figure 2 demonstrates that there was no clear relationship between concentrations of IFN-γ and hemoglobin, but that IL-17A levels were significantly higher in the more anemic patients, exhibiting a significant inverse correlation with hemoglobin (Rs=-0.49; P=0.034).…”

N-glycomic biomarkers of biological aging and longevity: A link with inflammaging

“…Lectins are invaluable tools for the study of glycosylation in normal and pathologic conditions, including inflammatory diseases (Tsuchiya et al, 1998). In particular, the sugar epitopes most relevant in inflammatory diseases and aging have been investigated in western blot or enzyme-linked assays using the following lectins: for ␣2,6-linked sialic acid, the lectin from Sambucus nigra (SNA) (Shibuya et al, 1987); for terminal galactose, Ricinus communis (RCA) (Barker et al, 1999;Parekh et al, 1985;Wong et al, 1993) or Erythrina cristagalli (ECL) lectins; for terminal GlcNAc, Bandeiraea simplicifolia II (BSA II) (Alavi et al, 2000;Croce et al, 2007;Sumar et al, 1991) or Psathyrella velutina (PVL) (Tsuchiya et al, 1993); for core fucosylation, Ulex europaeus I (UEA I) (Flogel et al, 1998;Gornik et al, 1999), Aspergillus oryzae (AOL) (Vanhooren et al, 2011) or Lens culinaris agglutinin (LCA) (Shinkawa et al, 2003); for bisecting GlcNAc, Phaseolus vulgaris E4 (PHA-E4) (Shinkawa et al, 2003).…”

Lyse or not to lyse: Clinical significance of red blood cell autoantibodies

“…It was shown that in vitro reduction of galactosylation enhances the pathogenicity of murine monoclonal IgG1 anti-RBC antibodies injected into mice in a complement-independent way [41]. Studies in several mouse models, however, did not give clear results, since the individual variation was high [42]. In humans, reduced Fc galactosylation of autoantibodies was observed in AIHA.…”