Regulatory CD4+CD25+FOXP3+ T-cells can be Converted into Cytotoxic Effectors (40.36)

Abstract

Abstract Background: Binding of the human IgM antibody B7-DC XAb to B7-DC on dendritic cells (DC) has profound immune modulatory effects. It enhances antigen presentation by DC, repolarizes T-helper (Th) 2 to Th1 cell responses, rapidly generates cytotoxic effectors and reprograms regulatory T-cells (Treg) into non-suppressive, cytokine producing autoimmune effectors. We hypothesized that co-culture of B7-DC XAb treated DC (DCXAb) with Treg results in the rapid generation of cytotoxic effectors. Methods: Bone marrow derived DC from wild type C57BL6 mice (WT-B6) were treated for 24 hours with either B7-DC XAb or a control human IgM antibody in the presence of melanoma cell lysate (B16). Subsequently, DCXAb were co-cultured with Treg (CD4+CD25+FOXP3+), Non-Treg (CD4+, CD25-), cytotoxic CD8+ T-cells isolated from WT-B6 mice and Treg from CD8 knockout mice (CD8 -/-). After re-isolation these T-cells were used in cytotoxic T-lymphocyte (CTL) assays targeting B16 and Thymic lymphoma (EL4) tumor cells. Results: Treg isolated from either WT-B6 mice or CD8 -/- mice co-cultured with B16 lysate treated DCXAb but not control antibody treated DC transformed into cytotoxic effectors targeting B16 but not EL4 tumor cells. Their level of cytotoxicity was comparable to that of CD8+ cells co-cultured with DCXAb. In contrast Non-Treg co-cultured with DCXAb did not kill in similar CTL assays. Conclusion: Co-culture of Treg with antigen treated DCXAb rapidly generates antigen specific cytotoxic effectors.