Work by Nina Reinart and colleagues has indicated a role for macrophage migration inhibitory factor (MIF) in the survival of chronic lymphocytic leukaemia (CLL) cells. Crossing a transgenic mouse model of CLL with Mif-knockout mice delayed leukaemogenesis, and this correlated with reduced numbers of macrophages in lymphoid organs. In vitro studies showed that the absence of MIF increases CLL cell sensitivity to apoptosis, and a MIF-specific antibody reduced the interaction between CLL cells and macrophages. Thus, MIF seems to promote the interaction between CLL cells and macrophages, increasing CLL cell survival.