ABSTRACT
Evidence of some degree of suppression of normal hematopoiesis has been observed in different types of malignancies. Investigations carried out in animals as well as humans have shown an inhibitory effect of leukemic cells on the growth of hematopoietic progenitors. Tumor necrosis factor, which was first described as an activity inducing hemorrhagic necrosis in tumor-bearing, B-cell growth factor-primed mice challenged with endotoxin, has since been shown to have multiple effects. It has been reported that interleukin-2, which is produced by several transformed cell lines inhibited the growth of murine granulomonocytic colony-forming unit. Colony suppression was not due to T cells or natural killer cells and did not seem to involve the participation of interferon. The inhibitory activities in various conditioned media or supernatants of leukemic cell cultures have not yet been characterized, and it cannot be excluded that the observed effect is related to the presence of one of the molecules.
