A disturbance of the IL-2/IL-2 receptor system parallels the activity of multiple myeloma

The IL-2/IL-2 receptor (IL-2R) system has been investigated in 64 patients with multiple myeloma (MM), 31 with monoclonal gammopathies of undetermined significance (MGUS) and 20 normal controls. The MM data were related to clinical status by comparing active disease, i.e. at diagnosis and at relapse, and stable disease, i.e. complete remission and off-treatment plateau phase. Serum and urinary values of the soluble IL-2R (sIL-2R) were significantly increased in MM patients compared with normal controls and this increase was related to activity. MM patients with active disease gave significantly higher values than those with stable disease. Compared with normal controls, enriched B cell (but not T cell) preparations from peripheral blood mononuclear cells (PBMC) showed significantly increased proportions of IL-2R+ cells in MM and MGUS. However, the highest proportions were detected in active MM compared with stable MM and MGUS. Also, 16% of all MM patients, as opposed to 9% of MGUS, had well-defined bone marrow IL-2R+ plasma cell populations. The lowest serum IL-2 values were found in active MM. Serial follow up of serum sIL-2R suggested that this peptide can be used as an additional marker of active malignancy. The data indicate that a disturbance of IL-2/IL-2R system is most pronounced in active MM. These findings may provide clues as to the T cell abnormalities in MM.