Analysis of Leu-7+ cell subpopulation in the peripheral blood of myeloma patients

Phenotypic heterogeneity and NK cell activity of lymphocyte subset expressing Leu-7 marker were investigated in 17 patients with myeloma and 20 age-matched controls. Co-expression of T cell antigen (Leu-1, Leu-3a and Leu-2a) on Leu-7+ cells was analyzed by two-color immunofluorescence, and the NK cell activity of peripheral lymphocytes was measured against 51Cr-labeled cell line K-562 (E/T:25). The proportion of Leu-7+ cells in the peripheral blood was higher in myeloma patients (31.5±10.3%, mean±1SD) than in control subjects (20.5±4.9%). Co-expression of Leu-1 or Leu-2a marker was increased on Leu-7+ cells in myeloma patients compared with normal controls (14.4±6.4% vs 7.3±4.3% for Leu-1; 17.0±7.3% vs 5.8±2.1% for Leu-2a). This indicated that the increase of OKT-8+/Leu-2a+ cells in myeloma patients, which was reported by us to be correlated with increase in serum monoclonal Ig levels, may be due to the Leu-7+ cell with Leu-2a. On the other hand, peripheral lymphocytes from myeloma patients and normal controls had similar NK cell activity (44.7±21.5%, 53.1±15.0%, respectively). These results suggest that the increased Leu-7+ cells co-expressing T antigen in myeloma patients had low NK cell activity. Since the Leu-7+ cells co-expressing Leu-2a marker are known to suppress Ig production of B-lymphocyte, the increase of them may be involved at least in part in the immunodeficiency of myeloma patients.