Abnormal blood monocytes in chronic lymphocytic leukemia.

Blood monocytes were analyzed in 28 patients with chronic lymphocytic leukemia without previous cytotoxic therapy and without recent infection. Using monoclonal antibodies and flow cytometry, monocytes identified by LeuM3 or My4 were low in percentage (2.3%), but absolute numbers were increased in many patients with values exceeding the normal range (120 to 510/microliter) in seven of 28 patients. Monocytosis was more prominent in patients with high leukemic counts, but there was no correlation to clinical stages. Monocytopenia was evident with less than 50 LeuM3+ cells/microliter in three patients. Two-color fluorescence was used for the analysis of cell surface expression of major histocompatibility complex (MHC) Class II molecules, complement receptors, and Fc receptors on the LeuM3+ monocytes. Compared to cells from control donors, there was an increase for MHC class II antigens, complement receptors, and Fc receptors on the monocytes in chronic lymphocytic leukemia, in terms of both the percentage of positive cells among the LeuM3+ monocytes and of fluorescence intensity. This increase was not restricted to patients with monocytosis nor were the molecules always upregulated concomitantly. The increase of antigen expression on LeuM3+ monocytes was more than 50% (1.5-fold) in seven of 22 patients for MHC Class II antigens, in seven of 16 patients for complement receptor and in six of 12 patients for Fc receptor. A similar decrease of antigen expression was observed only in one patient for MHC Class II and in one patient for complement receptor expression. Monocytosis and increased expression of monocyte cell surface antigens described for a large portion of patients might be causally involved in the immunodeficiency in chronic lymphocytic leukemia.