Immunoparesis in MGUS – Relationship of uninvolved immunoglobulin pair suppression and polyclonal immunoglobuline levels to MGUS risk categories
Abstract:
Monoclonal gammopathy of undetermined significance (MGUS) is an asymptomatic, potentially malignant condition. It has been established that annually approximately 1-2% of MGUS cases transforms into one of the malignant forms of monoclonal gammopathies. Progression risk factors include the quantity and type of M-protein, and namely the ratio of free light immunoglobulin chains (FLC). These factors, enable purposeful stratification of MGUS individuals. Some authors consider suppression of polyclonal immunoglobulin levels to be another progression factor. The aim of the study was to compare polyclonal immunoglobulin (PIg) levels with uninvolved heavy/light chain pair (HLC) levels in order to verify the degree of immunoparesis depending on MGUS risk category (0-3). The analyzed set consisted of 159 serum samples from MGUS patients (102 IgG, 57 IgA), who were stratified into 4 risk groups (0 – low, 1 – low-intermediate, 2 – high-intermediate and 3 – high risk of transformation). The results of analysis showed that with increasing degree of MGUS increases risk of immune paresis defined by decreasing levels of polyclonal immunoglobulins, ie. IgA and IgM in the case of IgG MGUS, respectively, IgG and IgM in case of IgA MGUS. Significant differences were also found when analyzing the levels of uninvolved HLC pairs IgG kappa (resp. IgG lambda) in IgG lambda (IgG kappa) dominant secretion. In the case of MGUS with IgA isotype, the results were similar. Discovery of the connection between the degree of immunosuppression and the level of MGUS risk contributes to our understanding of the relationship between biology, development and potential malignant transformation of MGUS. It is apparent that uninvolved HLC pair assay enables more reliable identification of at-risk MGUS patients than a simple quantitative assay for polyclonal immunoglobulins alone.