Effects of interferon treatment on the macrophage population in the bone marrow of patients with Ph1+-CML.

In Ph1+-CML the abnormal function of bone marrow stroma was related to the presence of clonally transformed macrophages (MAs). Moreover, previous in vitro studies revealed that activation (phagocytosis, cytotoxicity) of MAs was associated with a pronounced increase in alpha-D-galactosyl residues on their membranes. Stimulation of this cell population has been shown to be easily accomplished by interferon (IFN) treatment. The latter caused an enhanced expression of binding sites for the lectin Griffonia simplicifolia isotype I-B4 (GSA-I), specific for this carbohydrate moiety. The present immuno- and lectinhistochemical study was designed to quantify MA subsets of the bone marrow in patients with Ph1+-CML under IFN therapy. For comparison a control group with monotherapy by busulfan (BU) was included. Identification of the total MA population was carried out by a monoclonal antibody against CD68 (PG-M1) and for the characterization of its activated fraction, the lectin GSA-I was employed. In both therapeutic groups morphometric analysis revealed a conspicuous increase in PG-M1-positive MAs in sequential trephine biopsies. However, following IFN therapy the relative amount of the GSA-I fraction was maintained or even increased and accompanied by enhanced apoptosis. On the other hand, BU generated a significant reduction of this subpopulation and the number of apoptotic cells as well. This finding is probably related to the immunomodulatory activity of IFN associated with MA activation and secretion of biogenic mediators. These are thought to belong partly to the so-called tumor necrosis factor superfamily, which is known to stimulate programmed cell death (apoptosis).