Suppression of murine tumour growth through CD8⁺ cytotoxic T lymphocytes via activated DEC‐205⁺ dendritic cells by sequential administration of α‐galactosylceramide in vivo

Abstract

SummaryCancer immunity is mediated through the effective priming and activation of tumour‐specific class I MHC molecule‐restricted CD8+ cytotoxic T lymphocytes (CTLs). DEC‐205+ dendritic cells (DCs) can cross‐present the epitope(s) of captured tumour antigens associated with class I MHC molecules alongside co‐stimulatory molecules to prime and activate tumour‐specific CD8+ CTLs. Immunosuppressive tolerogenic DCs with reduced co‐stimulatory molecules may be a cause of impaired CTL induction. Hepa1‐6‐1 cells were established from the mouse hepatoma cell line Hepa1‐6; these cells grow continuously after subcutaneous implantation into syngeneic C57BL/6 (B6) mice and do not prime CD8+ CTLs. In this study, we show that the growth of ongoing tumours was suppressed by activated CD8+ CTLs with tumour‐specific cytotoxicity through the administration of the glycolipid α‐galactosylceramide (α‐GalCer), which is a compound known to stimulate invariant natural killer T (iNKT) cells and selectively activate DEC‐205+ DCs. Moreover, we demonstrated that sequential repetitive intraperitoneal inoculation with α‐GalCer every 48 hr appeared to convert tolerogenic DEC‐205+ DCs into immunogenic DCs with a higher expression of co‐stimulatory molecules and a stronger cross‐presentation capacity, which primed CTL precursors and induced tumour‐specific CD8+ CTLs within the tumour environment without activating iNKT cells. These findings provide a new basis for cancer immunotherapy to convert tolerogenic DEC‐205+ DCs within tumours into immunogenic DCs through the sequential administration of an immuno‐potent lipid/glycolipid, and then activated immunogenic DCs with sufficient expression of co‐stimulatory molecules prime and activate tumour‐specific CD8+ CTLs within the tumour to control tumour growth.

Differentiation of Langerhans Cells from Monocytes and Their Specific Function in Inducing IL-22–Specific Th Cells

“…Additionally, as we have reported recently using murine system, the known lipid Ag a-GalCer, which specifically stimulates invariant NKT cells, can also activate DCs through CD1d molecules and induce various cytokines to regulate the internal immune systems (16). Moreover, repetitive sequential stimulation with a-GalCer in the tumor-bearing mice preferentially activates DCs rather than invariant NKT cells, and the activated DCs elicit tumor-specific CD8 + CTLs to eliminate the tumor cells in vivo (14). Thus, tumor may be attacked after sequential stimulation of CD1d molecules on the DCs through their specific lipid ligands a-GalCer in the murine system.…”

Induction of tumor-specific CD8+ cytotoxic T lymphocytes from naïve human T cells by using Mycobacterium-derived mycolic acid and lipoarabinomannan-stimulated dendritic cells

“…We have recently reported that immunosuppressive tolerogenic DCs with down-regulated co-stimulatory molecules that will inhibit tumor-specific CTL induction have been observed within tumors and seem to be induced by tumor-derived soluble factors in both mice [1] and humans [2]. However, intravenous treatment with tumor-specific MHC molecule-restricted CD8 + CTLs showing excellent in vitro cytotoxicity against tumors in mice has proven ineffective for tumor mass regression [3]. This may be because tolerogenic DCs inactivate the cytotoxicity of administered CTLs in vivo.…”

“…By contrast, internally synthesized antigenic molecules, such as viral components or tumor antigens, are presented by class I MHC molecules [4]. As shown in previous research [1, 5], it seems that most DEC-205 + DCs within the murine tumor mass became tolerogenic with down-regulated expression of co-stimulatory molecules despite the unique cross-presentation function of these DCs [3, 6, 7]. This function involves the CTL epitope within the externally captured antigens being presented with the class I MHC, and we have previously reported that such cross-presentation occurs after immunizing with proteins that have unique adjuvants, such as immune stimulating complexes (ISCOMs) [8] or cholera toxin [9].…”

“…Nevertheless, even if tumor-derived fragments are captured by neighboring DEC-205 + DCs that possess cross-presentation, and those tolerogenic DCs expressed processed tumor epitope(s) associated with class I MHCs with insufficient co-stimulatory molecules, tumor-specific CD8 + CTLs are unable to be primed from naïve CD3 + T cells in an MHC-restricted manner. However, as we have recently reported in a murine model [3], we can convert tolerogenic DEC-205 + DCs into immunogenic DCs in vivo using sufficient co-stimulatory molecules and sequential repetitive administration with immuno-potent lipid/glycolipids, such as α-galactosylceramide (α-GalCer), to their CD1d-molecules. Activated immunogenic DEC-205 + DCs within the tumor mass present tumor antigens associated with MHC-I that prime tumor-specific CD8 + CTLs.…”

Pectate Lyase Promoting Streptolysin O Expression in Escherichia coli and Strengthening Its Activity

“…The antigenicity of proteins was determined by antigenic determinants and the antigenic determinants of the proteins had 2 types of sequential epitope (24,25) and conformation epitope (26). The research showed that the purified PEL-SLO fusion protein had a specialty of 1 × 10 7 HU/mg, about 10 fold of natural SLO.…”