Circulating levels of soluble CD23 reflect clinical and biological features of leukemic B-cell chronic lymphoproliferative disorders

Summary One hundred and twenty-four sera, from patients with various leukemic B-cell chronic lymphoproliferative diseases were investigated at diagnosis by ELISA for their soluble CD23 content. Immunophenotyping was carried out in all patients, and in a selected subset the mean number of membrane-bound CD23 molecules per cell was also investigated. Seventy-three patients had typical B chronic lymphocytic leukenia, 41 leukemic B-cell disorders with atypical morphological and/or immunophenotypic features, 5 had low-grade follicular cell lymphoma in the leukemic phase, and 5 had splenic lymphoma with villous lymphocytes Soluble CD23 levels were significantly higher than in normal sera (mean±SD: typical B chronic lymphocytic leukemia 3,650±4,654 U/ml, atypical B chronic lymphocytic leukemia 3,440±4,671 U/ml, follicular cell lymphoma 3,200±1,511 U/ml, splenic lymphoma with villous lymphocytes 8,236±7,294 U/ml, controls 137±128 U/ml;P<0.001). More advanced Rai's stages were related to higher soluble CD23 levels (P<0.01), both in typical and atypical B chronic lymphocytic leukemias, the highest levels and the best correlation with the absolute number of circulating CD19+ cells (r=0.50) being observed in the typical form. The number of membrane-bound CD23 molecules per cell was significantly higher in typical than in atypical B chronic lymphocytic leukemias (mean number 156,727±94,668 vs. 12,010±10,643,P<0.001). Our data suggest that soluble CD23 levels correlate with the clinical and biological features of leukemic B-cell lymphoproliferative disorders.