The progress in translating fundamental immunological advances into new effective therapeutic interventions has been quite extraordinary. We have been using our knowledge of dendritic cell (DC) surface molecules and monoclonal antibodies to develop new therapeutic strategies to treat cancer. The preclinical development and clinical application of these strategies depends heavily on flow cytometry. Its use to investigate CD83 as a novel target for a new human therapeutic antibody has revealed new biology and confirmed efficacy in non-human primates. Detailed flow studies have defined CD300f epitopes and validated the DCR-2 monoclonal antibody as a potential first step in evaluating a therapeutic antibody for treating acute myeloid leukaemia and generating therapeutic derivatives such as BiTEs or CAR-T cells.  Similarly, flow analysis of DC cross-presentation using highly specific antibodies and specific tumour antigen T cell responses has guided our work, using a new human IgG4 chimeric CMRF-56 antibody to isolate blood DC for therapeutic cancer vaccination.