In vitro cytokine-primed leukaemia cells induce in vivo T cell responsiveness in chronic myeloid leukaemia.

We previously showed that in chronic myeloid leukaemia (CML), it is possible to induce costimulatory molecules, CD80/CD86, on leukaemia cells by culturing adherent peripheral blood mononuclear cells from these patients with IL-4 and GM-CSF. In addition to the expression of CD80/CD86 molecules, some of the leukaemia cells also expressed the dendritic cell marker, CD1a. When these leukaemia cells were used in mixed lymphocyte leukaemia reactions, they mediated autologous T cell proliferation not seen when fresh leukaemia cells were used as the stimulator cells. In this study, we showed that reinfusion of these immunogenic leukaemia cells to the autologous hosts resulted in priming in vivo of T cells so that they could respond to subsequent rechallenge in vitro with fresh autologous leukaemia cells. Although cytotoxic T cells against leukaemia cells were not demonstrated, these T cells could proliferate and produce interferon-y when cocultured in vitro with the leukaemia cells. Our findings therefore provide further evidence for the immunogenicity of these cultured leukaemia cells in CML.