Immunoglobulin A1 (IgA1)

IgA1 protein isolated from patients with IgA nephropathy (IGAN1) were galactosylated to a lesser degree compared to controls. The galactose deficiency was in the O-linked side chains located in the hinge region of the IgA1 molecule. Incompletely galactosylated IgA1 was detected in complexes with IgG, supporting the hypothesis that the formation of abnormal IgA1-IgG complexes impairs the rate of elimination and hepatic catabolism of IgA1 in patients with IgA nephropathy. The signal peptide and first 2 extracellular residues of IRTA1 are fused to the extracellular spacer, transmembrane domain, and cytoplasmic tail of the membrane IgA1 receptor (IGHA1) in the FR4 multiple myeloma (MM) cell line, but not in other MM or lymphoma cell lines. They concluded that the IRTA1-IGHA1 fusion may be a rare event in B-cell malignancy.