Generation in vitro of B-cell chronic lymphocytic leukaemia-proliferative and specific HLA class-II-restricted cytotoxic T-cell responses using autologous dendritic cells pulsed with tumour cell lysate

Immunotherapy using dendritic cells has shown encouraging results in both h aematological and non-haematological malignancies. In this study, monocyte- derived dendritic cells from patients with B-CLL were cultured for 6 days i n the presence of IL-4 and GM-CSF. Autologous B-CLL T-cells were cultured a lone or with B-CLL lysate-pulsed and unpulsed autologous dendritic cells. I FN-gamma secretion was assessed using ELISA. Cytotoxicity was assessed, aft er 21 days in culture and re-stimulation, using flow cytometry with and wit hout blockade by anti-HLA class I, anti-HLA class II, anti-CD4, anti-CD8 an d anti-TCR alpha beta monoclonal antibodies. B-CLL T cells stimulated with B-CLL lysate-pulsed autologous dendritic cells showed a significant (P = 0. 0004) increase in IFN-gamma secretion and a significant (P = 0.0008) increa se in specific cytotoxicity to autologous B-cell targets, but none to autol ogous T cell or B cell targets from healthy individuals. B-CLL T cells cult ured with (non-B-CLL) B-cell lysate-pulsed B-CLL dendritic cells showed no significant response. Pulsing dendritic cells from healthy volunteers with an autologous (non-B-CLL) B-cell lysate did not stimulate proliferation, cy tokine production or cytotoxicity by autologous T cells. Pulsing B-CLL dend ritic cells with allogeneic B-CLL lysates and culturing with autologous T-c ells elicited cytotoxicity against autologous B-CLL targets in some cases, but not in others. Cytotoxicity was significantly reduced by blocking with anti-HLA class II (P = 0.001), anti-TCR alpha beta (P = 0.03) and anti-CD4 (P = 0.046) antibodies. Phenotyping of the responding T-cell population dem onstrated the majority to be CD4 positive. Our data demonstrate that HLA cl ass II-restricted proliferative and cytotoxic T-cell responses to B-CLL can be generated using autologous dendritic cells pulsed with tumour cell lysa te.