Phenotypic and functional deficiencies of leukaemic dendritic cells from patients with chronic myeloid leukaemia

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Abstract
Summary. Chronic myeloid leukaemia (CML) dendritic cells (DC) are possible candidates for inducing antileukaemic immunity. This study aimed to investigate the frequency, phenotype and function of blood‐derived leukaemic DC in comparison with DC from healthy donors using flow cytometric assays and mixed leucocyte reaction (MLR). Immature leukaemic DC displayed a reduced endocytotic capacity as compared with healthy controls. Moreover, in vitro maturation of leukaemic DC was found to be deficient. Expression of CD80, CD83, CD86, and major histocompatibility complex class I and class II antigens were reduced on lipopolysaccharide (LPS)‐matured leukaemic DC but were enhanced by a mixture of interleukin 1β (IL‐1β), IL‐6, tumour necrosis factor‐α (TNF‐α) and prostaglandin E2 (PGE2). Upon stimulation with bacterial LPS, intracellular TNF‐α and IL‐8 production was diminished in maturing DC from CML patients. This distinct cytokine deficiency was overcome when leukaemic DC were stimulated with cytokines/PGE2. MLR showed fully functional leukaemic DC after TNF‐α‐induced maturation, but a reduced proliferative alloresponse of leukaemic peripheral blood mononuclear cells. Further, intracellular production of cytokines in CML‐derived T cells was markedly reduced. These data indicated that, in CML, the maturation response of leukaemic monocyte‐derived DC to a natural stimulus like LPS is abnormal and may be caused by an aberrant TNF‐α response in these cells. Thus, TNF‐α alone or in combination with pro‐inflammatory and T‐cell stimulatory cytokines should be considered as an adjuvant for DC‐based immunotherapy in CML.

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