Expression and regulation of tumor necrosis factor, interleukin-2, and hematopoietic growth factor receptors in B-cell chronic lymphocytic leukemia

Leukemic cells from patients with B-cell chronic lymphocytic leukemia (B- CLL) express tumor necrosis factor (TNF) and interleukin-2 (IL-2) receptors, but only a low proliferative response can be elicited in vitro by TNFα and IL-2. To investigate the functional properties of IL-2 and TNFα on leukemic B cells, we evaluated (1) the regulation of expression of TNF receptors (TNF- R) and IL-2 receptors on leukemic B cells after culture with TNFα and IL-2; (2) the effect of the combination of TNFα and IL-2 in a proliferative in vitro assay; and (3) the expression and regulation by these cytokines of receptors for hematopoietic factors, including IL-3, granulocyte colony- stimulating factor (G-CSF), and granulocyte-macrophage colony-stimulating factor (GM-CSF). Flow cytometry analysis showed that freshly isolated leukemic cells from B-CLL patients bear the 75-kD TNF-R and the 55-kD IL-2R; TNFα was able to upregulate the 55-kD IL-2R but not the 75-kD TNF-R. On the other hand, IL-2 was not able to modify the expression of the above-mentioned receptors. Although each cytokine alone was unable to induce a relevant proliferation of leukemic cells, a synergistic proliferative effect was detected when these cytokines were used in combination. Leukemic B cells from B-CLL patients bear receptors for hematopoietic factors (IL-3, G-CSF, and GM- CSF) that were upregulated in vitro by IL-2 via the 55-kD IL-2R. On the contrary, TNFα was unable to affect the expression of the above-mentioned receptors. These results indicate (1) that IL-2 and TNF receptors are related to each other on leukemic cells in B-CLL and (2) that the IL-2R is involved in the regulation of other structures, ie, CSF receptors, thus pointing to another functional role of this receptor complex and the related cytokine in leukemic cells.