IgA monoclonal gammopathies are accompanied by higher total TGF‐β1 levels than IgG or IgM monoclonal gammopathies

The progression of monoclonal gammopathies is affected by a range of factors, including the microenvironment surrounding plasma cells. It is recognized that TGF-β1 plays a distinct role in stimulating IgA production. Hence, this study aims to investigate whether individuals with serum IgA monoclonal immunoglobulins (paraproteins) exhibit elevated total TGF-β1 levels compared to those with IgG or IgM paraproteins. To achieve this goal, individuals with a positive laboratory finding of monoclonal gammopathy were segregated according to the paraprotein class as well as according to the type of the light chain. Total TGF-β1 levels were assessed in blood serum samples containing IgG (n = 50), IgA (n = 46), and IgM (n = 31) paraproteins. Elevated level of TGF-β1 was confirmed in sera with IgA paraproteins (median 25.8 ng/mL; interquartile range IQR: 19.0-33.7) compared to those having IgG (median: 18.2 ng/mL; IQR: 14.3-22.1; p < 0.001) or IgM paraproteins (21.5 ng/mL; IQR: 15.0-27.4; p = 0.043). Also, a higher TGF-β1 level was detected in sera with IgMλ than those with IgMκ paraproteins (p = 0.043). This research affirms the role of TGF-β1 in the pathophysiology of IgA monoclonal gammopathies and the potential switch towards the IgA isotype, known for a less favourable prognosis.