The use of dendritic cells (DCs) loaded with tumour antigen is one of the most promising approaches to induce tumour-specific immune response. However, methods of the vaccine preparation have not yet been standardized. The purpose of the study was to analyse the anti-tumour efficacy of tumour antigen-loaded mouse bone marrow-derived dendritic cells (BM-DC/TAg) at different maturation stages. BM-DCs were loaded with MC38 colon carcinoma cell lysate (TAg) alone, to become partially differentiated, or were additionally stimulated with inflammatory cytokines such as TNF-α, IFN-γ, or IL-12 to reach complete maturity. BM-DCs simultaneously stimulated with TAg and cytokines (especially IL-12 or IFN-γ+IL-12) were in vitro more effective immune response activators than BM-DC/TAg cells. However, the highest anti-tumour effect in vivo was noted when mice were treated just with BM-DC/TAg. In a further study, the ability of IL-12 gene transduced BM-DCs (BM-DC/IL-12) to augment the immune response induced by BM-DC/TAg cells at different stages of maturation was examined. The highest anti-tumour effect was observed when partially differentiated BM-DC/TAg cells were injected simultaneously with BM-DC/IL-12 cells. The results suggest that partially differentiated BM-DC/TAg cells are more potent in evoking a strong anti-tumour response in vivo than mature BM-DCs. Moreover, the capacity of BM-DC/TAg cells for further differentiation and their sensitivity to factors secreted in vivo by the host or cells engineered to cytokine production seem to be of great importance.

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