Dendritic Cells Charged with Apoptotic Tumor Cells Induce Long-Lived Protective CD4+ and CD8+ T Cell Immunity against B16 Melanoma

Abstract

Dendritic cells (DCs) are potent APCs and attractive vectors for cancer immunotherapy. Using the B16 melanoma, a poorly immunogenic experimental tumor that expresses low levels of MHC class I products, we investigated whether DCs loaded ex vivo with apoptotic tumor cells could elicit combined CD4+ and CD8+ T cell dependent, long term immunity following injection into mice. The bone marrow-derived DCs underwent maturation during overnight coculture with apoptotic melanoma cells. Following injection, DCs migrated to the draining lymph nodes comparably to control DCs at a level corresponding to ∼0.5% of the injected inoculum. Mice vaccinated with tumor-loaded DCs were protected against an intracutaneous challenge with B16, with 80% of the mice remaining tumor-free 12 wk after challenge. CD4+ and CD8+ T cells were efficiently primed in vaccinated animals, as evidenced by IFN-γ secretion after in vitro stimulation with DCs loaded with apoptotic B16 or DCs pulsed with the naturally expressed melanoma Ag, tyrosinase-related protein 2. In addition, B16 melanoma cells were recognized by immune CD8+ T cells in vitro, and cytolytic activity against tyrosinase-related protein 2180–188-pulsed target cells was observed in vivo. When either CD4+ or CD8+ T cells were depleted at the time of challenge, the protection was completely abrogated. Mice receiving a tumor challenge 10 wk after vaccination were also protected, consistent with the induction of tumor-specific memory. Therefore, DCs loaded with cells undergoing apoptotic death can prime melanoma-specific helper and CTLs and provide long term protection against a poorly immunogenic tumor in mice.

Cross‐presentation of antigens from apoptotic tumor cells by liver sinusoidal endothelial cells leads to tumor‐specific CD8+ T cell tolerance

“…Meanwhile, it became clear that immune responses can be generated outside secondary lymphatic tissue [23,32] and that tumors are not simply ignored by the immune system even if they grow at extra-lymphatic sites [33]. Cross-presentation of tumor-associated antigens by DC rather than direct antigen presentation by tumor cells is operative in recognition of tumor cells by the immune system and induction of immunity or tolerance [34][35][36]. However, processing of tumor antigens critically depends on DC subtype and on the mode of antigen delivery [37,38].…”

“…Another important determinant of tumor-specific T cell responses is the functional state of the antigen-presenting DC. Activated, mature DC promote tumor immunity [34], whereas immature DC rather favor development of T cell tolerance towards tumor-associated antigens [39]. Moreover, uptake of apoptotic cell material itself leads to a hypo-reactive state of DC [40].…”

Rapid and efficient nonviral gene delivery of CD154 to primary chronic lymphocytic leukemia cells

“…It was reported previously that apoptotic bodies were favorable for DC presenting tumor antigens. [48][49][50][51][52] Therefore, apoptosis of the CD154-tranfected cells after administration in vivo may even be favorable for immunotherapy. Human clinical studies are underway to determine the effectiveness of CD154-transfected B-CLL cells in producing in vivo immune responses.…”

Enhanced T-cell immunity induced by dendritic cells with phagocytosis of heat shock protein 70 gene-transfected tumor cells in early phase of apoptosis

“…14 More recently, it has further been shown that DC charged with apoptotic tumor cells induced long-lived protective CD4 þ and CD8 þ T-cell immunity 15 and apoptotic, but not necrotic, tumor cells are efficient vaccines in vivo. 16 Apparently contradicting these results, it has also been reported that the presence of apoptotic cells during macrophage activation increases their secretion of anti-inflammatory mediators 17 and decreases their secretion of proinflammatory cytokines, 18 and that apoptotic cells are actually able to induce suppression of inflammatory responses and tolerance. 19,20 In line with this notion, there is evidence for the lack of immunogenicity 21 or reduced immunogenicity of apoptotic tumor cells as compared with viable counterparts.…”