T-CELL STIMULATION-INDUCED BY IDIOTYPES ON MONOCLONAL IMMUNOGLOBULINSIN PATIENTS WITH MONOCLONAL GAMMOPATHIES

The stimulation of peripheral blood mononuclear cells by purified auto logous and/or allogeneic monoclonal IgG was studied in five patients w ith multiple myeloma (MM), nine patients with monoclonal gammopathy of undetermined significance (MGUS) and six healthy individuals. Single cells secreting IFN-gamma or IL-2 were identified using an enzyme-link ed immunospot assay. Patients' cells were preferentially stimulated by autologous monoclonal IgG at low concentrations (1-100 pg/ml), while 100 ng/ml or higher stimulated T cells both from patients and, to a le sser degree, healthy individuals. This biphasic dose-response of T-cel l stimulation by autologous monoclonal IgG was reproduced in all patie nts. The numbers of cells secreting IFN-gamma and IL-2 in response to allogeneic IgG were significantly lower than the numbers obtained usin g autologous IgG in patients with MM and MGUS. Cells from healthy indi viduals were stimulated by allogeneic monoclonal IgG, but to a lesser extent. The results of this study support the presence of idiotype-rea ctive T cells in patients with-MM and MGUS and also may suggest a gene ral but less pronounced T-cell reactivity to monoclonal IgG among thes e patients.