Structural characteristics and terminal galactose expression of monoclonal IgA paraproteins from sera of multiple myeloma patients

Abstract

IgA myeloma accounts for approximately 20% of all myeloma cases and is generally associated with a less favorable prognosis than other subtypes. Some complications specific to IgA myeloma might be linked to the structural features of monoclonal IgA. These include a high degree of polymerization, which can cause hyperviscosity syndrome, and reduced expression of galactose (Gal) residues on the glycans of the IgA hinge region, leading to IgA deposition and nephropathy. To assess the level of polymerization and galactose expression, we isolated IgA from the sera of 15 myeloma patients using affinity chromatography on Protein M agarose. Non-reducing SDSPAGE revealed two or more fractions, with molecular weights of 160 kDa and higher. Western blot analysis confirmed the presence of IgA monomers and dimers in all samples. Galactose expression was evaluated by lectin blotting using Ricinus communis agglutinin I (RCA I), a Dgalactose-binding lectin. RCA I blotting demonstrated that both monomeric and polymeric IgA forms expressed galactose, although the intensity notably varied among samples. Our results suggest that the structural properties of myeloma IgA are heterogeneous. To determine whether these differences influence disease progression, we plan to correlate IgA structural features with patients’ clinical data. Further, in-depth glycoprotein analyses will be carried out using mass spectrometry in collaboration with the Horizon CanSERVBeCELS 2025: Belgrade Conference for Early-Career Life Scientists, taking place on Friday, September 5, 2025, at the Institute of Molecular Genetics and Genetic Engineering (IMGGE) in Belgrad