Antitumor activity in vitro in chronic myelogenous leukaemia revealed after treating peripheral cells with cytosine arabinoside

Human CD4+ T cell clone longevity in tissue culture: lack of influence of donor age or cell origin

CD4+ human T cell clones were derived from activated peripheral blood lymphocytes of healthy young adults to establish cloning efficiencies (CE) and clonal longevities. These results were compared with those obtained using cells from the very elderly, also in excellent health. CE and both maximal and average longevities under appropriate culture conditions were very similar in the two groups. Moreover, CE of CD34+ hematopoietic progenitor cells and longevities of clones derived from them were also similar. Finally, CE and longevities of clones derived from a patient with chronic myelogenous leukaemia were found to be comparable as well. Hence, T cells with absolutely no antigenic exposure in vivo prior to cloning (i.e. CD34-derived) and those potentially exposed to chronic antigenic stimulation (CML-derived) and those from young or old donors all had similar cloning and propagation properties in vitro. These results imply that the longevity of T cells in culture is more likely to be dictated by cloning conditions than any intrinsic differences between the cells studied.

Recognition of chronic myelogenous leukaemia cells by autologous T lymphocytes primed in vitro against the patient's dendritic cells

Defects in immune responses are common in patients with chronic myelogenous leukaemia (CML). However, using dendritic cells (DCs) to promote T-cell immunity in vitro may nonetheless elicit potent specific anti-tumour responses for use in immunotherapy. Here, we show that DCs generated from CML patients had a typical dendritic phenotype and were able to stimulate autologous T cells. Three primed T-cell lines were studied in more detail in one patient. They were stimulated by autologous CML cells, but not by normal non-leukaemic cells from the patient's HLA-identical sibling. This was blocked by HLA-DR-specific, but not HLA-DQ- or HLA-DP-specific antibodies. CML-stimulated cytokine secretion, including interferon-gamma and granulocyte macrophage-colony stimulating factor, suggested a Th1-type phenotype for these sensitized anti-leukaemic T cells. This study therefore shows that cells with a functional dendritic phenotype can be generated from the blood of CML patients and are potent inducers of T-cell responses to tumour cells. This approach allows sensitization of patients' T cells by their own particular tumour without the need to identify the exact leukaemia antigens involved, and may find application in immunotherapy of CML.