Differential expression of glycogenes in tonsillar B lymphocytes in association with proteinuria and renal dysfunction in IgA nephropathy

Aberrant O-glycosylation of serum and tonsillar IgA1 is one of the main pathogeneses of IgA nephropathy (IgAN). However, the synthesis of underglycosylated IgA1 in tonsils has not yet been characterized. This study examined tonsillar B lymphocytes of IgAN (n = 34) using tonsils derived from patients with chronic tonsillitis (n = 24) and sleep apnea syndrome (n = 14) as a control. Gene expression of β1,3-galactosyltransferase (β3GalT), and the core 1 β3GalT-specific molecular chaperone, Cosmc, UDP-N-acetyl-α-D-galactosamine: polypeptide N-acetylgalactosaminyl-transferase 2, were significantly decreased in tonsillar CD19-positive B lymphocytes from IgAN patients compared to control tonsillar tissues as determined by real-time RT-PCR. Tonsillar B cell β3GalT gene expression significantly correlated with estimated GFR and negatively correlated with proteinuria and histological injury score. Western blotting showed the protein expression of β3GalT in the tonsils to significantly decrease in IgAN in comparison to the controls. These data suggest the downregulation of β3GalT in tonsillar B lymphocytes to be closely associated with the clinical characteristics of IgAN.