CD28 and B-cell chronic lymphocytic leukemia: The loss of CD28 expression on B-CLL T cells may be also related to the influence of the elevated TNF-alpha serum levels produced by neoplastic B lymphocytes and T cells in patients with B-CLL (Adami et al, 1994; Bojarska-Junak et al, 2002; Gallego et al, 2003).