Protection of mice against leukemia after vaccination with bone marrow-derived dendritic cells loaded with apoptotic leukemia cells.

Dendritic cells (DCs) are professional antigen-presenting cells (APCs) that need to be activated before they can function to initiate primary and secondary immune responses in vivo. DCs are also specialized to maintain peripheral tolerance to self after uptake of apoptotic material, likely corresponding to both apoptotic bodies and whole apoptotic cells. Here, we report that murine bone marrow-derived DCs can be activated in vitro by exogenous signals received from apoptotic leukemia cells expressing on the cell surface a model tumor-associated antigen. Injected in vivo, these exogenously activated DCs can function as adjuvants to protect mice against leukemia by stimulating an antigen-specific cellular-mediated cytotoxic immune response. To our knowledge, this is the first report indicating that DCs loaded with apoptotic leukemia cells protect mice against leukemia development.