Abstract
Objective : IgA1 molecules display abnormal O-glycosylation of the hinge region in patients with IgA nephropathy (IgAN). Several studies have proposed that increased production of Th2 cytokines and functional abnormality of the enzyme (core1 β1, 3-galactosyltransferase : C1 β 3Gal-T) responsible for O-glycosylation of IgA1 might be the mechanism involved in the altered glycosylation of IgA1. However, these mechanisms have not yet been clearly elucidated. To assess the effect of T cell cytokines on IgA1 glycosylation, we analyzed the mRNA expression of both C1 β3 Gal-T and its molecular chaperone Cosmc, and glycosylation of IgA1 secreted from the human B cell line with stimuli of these cytokines.
Materials & Methods : The human B lymphoma cell line, DAKIKI, which shows surface expression of IgA1, was cultured with recombinant human IFN-γ, IL-4 and IL-5 for 5 days to analyze cell proliferation, and the production and glycosylation of IgA1. The production and glycosylation of IgA1 were determined by sandwich ELISA and enzyme-linked lectin binding assay, respectively.Real-time PCR was performed to measure the mRNA expression of C1 β 3 Gal-T and Cosmc in cells with IFN-γ and IL-4 stimuli after 12 and 48 hours.
Results : IL-4 or IL-5 stimulation induced significantly greater cell proliferation than IFN-γ stimulus or control. IgA1 concentration in supernatant from IL-4-stimulated cells was significantly higher than those in supernatant from cells stimulated by other cytokinesand control cells. IL-4 stimulation significantly decreased the mRNA expression of both C1 β 3Gal-T and Cosmc, and altered the terminal glycosylation of secreted IgA1.
Conclusion : It appears that Th2 cytokines induced B cell proliferation and IL- 4 may affect mRNA expression of both C1 β 3Gal-T and Cosmc, and subsequently altered the glycosylation of IgA1.
