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. [ABSTRACT FROM AUTHOR]