Constitutive production of a non-interferon macrophage activating factor by HTLV-transformed T cells

Culture supernatants of several human T cell leukemia virus infected cell lines were assessed for the induction of tumoricidal activity against human melanoma target cells in a 72-hr assay. Two cell lines, MT-2 and C10/MJ2, were found to produce high levels of MAF activity constitutively. However, the MT-2 cell line, unlike C10/MJ2, produced little interferon. MT-2 MAF was distinct from interferon-gamma by a number of biochemical and serological criteria. The MAF activity was associated with a non-glycosylated, acid stable protein which has an apparent molecular weight of 55,000 and an isoelectric point of 5.5. Furthermore, this molecule is not related to any of the known lymphokines or cytokines such as the interleukins or colony stimulating factors.