Monoclonal antibody-defined T lymphocyte subpopulations in monoclonal gammapathy of undetermined significance.

We used monoclonal antibodies of the OK series to study T lymphocyte subpopulations in 55 patients with monoclonal gammapathy of undetermined significance (MGUS) and in 40 healthy control subjects, with the aim to investigate if alterations in T lymphocyte subpopulations occur also in MGUS. Mean OKT3+ and OKT8+ cell counts were higher (p less than 0.01 and p less than 0.001, respectively) and the mean OKT4/OKT8 ratio was lower (p less than 0.02) in MGUS patients than in the control subjects. MGUS with the IgM-type monoclonal immunoglobulin (IgM-MGUS) showed the most evident derangement of T lymphocyte subpopulations, i.e., a significant increase of OKT8+ cells and a significant reduction of the OKT4/OKT8 ratio. OKT4+ and OKT8+ cells were significantly increased in patients with high paraprotein concentration (above 16 g/l). Our data suggest that alterations of T lymphocytes are present in MGUS, and that they are similar to those observed in malignant lymphoproliferative disorders.