Does IL-2 receptor expression and secretion in chronic B-cell leukemia have a role in down-regulation of the immune system?

Recent evidence of cell membrane expression of interleukin-2 receptors (IL-2R) by malignant B cells in hairy cell leukemia (HCL) and B-chronic lymphocytic leukemia (B-CLL) has lead to speculation that growth factors, such as IL-2, may play a role in the pathophysiology of these diseases. However, to date, it is not clear that IL-2 is a consistent growth factor in vitro or in vivo for malignant B cells. What then is the potential significance of membrane IL-2R on the malignant B-cell membrane? Laboratory analysis indicates that the malignant cells are the source of elevated serum levels of soluble Tac protein (sIL-2r alpha) in both diseases. Indeed, these cells spontaneously secrete sIL-2R alpha into culture medium. We speculate that the presence of an expanding mass of malignant B cells possessing high and low affinity membrane IL-2R may contribute significantly to the associated immunodeficiency seen in B-CLL. In particular, it is the cell associated high affinity IL-2R that have the greatest potential for reducing the levels of free IL-2 available to normal immune cells.