Idiotype-reactive T-cell subsets and tumor load in monoclonal gammopathies

The presence of idiotype-reactive T-cell subsets and their relation to the tumor load were analyzed in 9 patients with monoclonal gammopathy of undetermined significance (MGUS), in 12 patients with multiple myeloma (MM) clinical stage I, and in 9 patients with MM stage II/III. An enzyme-linked immunospot assay was used to identify interferon-χ, (IFN-χ)-, interleukin- 2 (IL-2)-, or IL-4-secreting T cells after stimulation by F(ab')₂ fragments of monoclonal IgG. The response to autologous IgG was significantly higher than that induced by isotypic monoclonal IgG. Comparable results were obtained in a proliferation assay (³H-thymidine incorporation). A total of 8 of 9 patients with MGUS, 7 of 12 patients with MM stage I, and 3 of 9 with MM stage II/III had T cells secreting IFN-γ and/or IL-2 (T helper [Th1] type-1 cells), whereas cells secreting both Th1 and Th2 or Th0 types of cytokines were more frequent in patients with MM, particularly in those with MM stage II/III. The number and frequency of Th1-type cells were significantly higher in MGUS patients as compared with those of MM stage II/III. The T-cell response was inhibited by an anti-DR antibody. The results indicate that idiotype-reactive T cells of the Th1 and Th2 or Th0 subsets were present in MGs and might provide indirect evidence that idiotype-reactive Th1-type cells may have a regulatory impact on the human tumor B cells.