Langerin+CD8α+ Dendritic Cells Are Critical for Cross-Priming and IL-12 Production in Response to Systemic Antigens

Abstract

Distinct dendritic cell (DC) subsets differ with respect to pathways of Ag uptake and intracellular routing to MHC class I or MHC class II molecules. Murine studies suggest a specialized role for CD8α+ DC in cross-presentation, where exogenous Ags are presented on MHC class I molecules to CD8+ T cells, while CD8α− DC are more likely to present extracellular Ags on MHC class II molecules to CD4+ T cells. As a proportion of CD8α+ DC have been shown to express langerin (CD207), we investigated the role of langerin+CD8α+ DC in presenting Ag and priming T cell responses to soluble Ags. When splenic DC populations were sorted from animals administered protein i.v., the ability to cross-present Ag was restricted to the langerin+ compartment of the CD8α+ DC population. The langerin+CD8α+ DC population was also susceptible to depletion following administration of cytochrome c, which is known to trigger apoptosis if diverted to the cytosol. Cross-priming of CTL in the presence of the adjuvant activity of the TLR2 ligand N-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-[R]-Cys-[S]-Serl-[S]-Lys4-trihydrochloride or the invariant NKT cell ligand α-galactosylceramide was severely impaired in animals selectively depleted of langerin+ cells in vivo. The production of IL-12p40 in response to these systemic activation stimuli was restricted to langerin+CD8α+ DC, and the release of IL-12p70 into the serum following invariant NKT cell activation was ablated in the absence of langerin+ cells. These data suggest a critical role for the langerin+ compartment of the CD8α+ DC population in cross-priming and IL-12 production.

Targeted Delivery of α-Galactosylceramide to CD8α+ Dendritic Cells Optimizes Type I NKT Cell–Based Antitumor Responses

“…DCs from the spleen are heterogeneous, and recent studies suggested that DC subsets could differ in their ability to stimulate iNKT cells (26,45,46). For example, we have previously reported that among the CD8a 2 DC subset, CD4 2 DCs were more efficient at activating iNKT cells, relative to CD4 + DCs (45).…”

“…In the mouse system, DCs in the spleen, an important site of immune responses to blood-borne Ag, are mainly composed of CD8a + DCs, a subset specialized in Ag crosspresentation, and of CD8a 2 DCs, a subset more efficient at presenting Ag on MHC class II (24). Recent findings indicated that CD8a + DCs are particularly potent to activate iNKT cells (25) and to trigger iNKT cell-based innate immune responses (26,27). These data, and the fact that CD8a + DCs excel in Ag crosspresentation, prompted us to actively deliver a-GalCer and Ag to CD8a + DCs in vivo.…”

An autologous leukemia cell vaccine prevents murine acute leukemia relapse after cytarabine treatment

“…lang-EGFP hosts were used to identify langerin The interaction between DCs and NKT cells involves CD40-CD40 ligand interaction that contributes to significant production of IL-12, primarily from langerin 1 CD8a 1 DCs. 44 Serum IL-12 was analyzed 5 hours after vaccine administration in the presence or absence of established leukemia, and similar levels were observed ( Figure 2L). Together, these results indicate that the inefficacy of the vaccine was not attributed to a failure to activate NKT cells or DCs.…”

“…[44][45][46] To establish whether langerin 1 DCs were involved in the protection afforded by the leukemia/a-GalCer vaccine, lang-EGFPDTR hosts were depleted of langerin-expressing cells by DT treatment before vaccination, as previously described. 44 This led to complete abrogation of the protective effect of leukemia/a-GalCer ( Figure 1F), indicating that langerin 1 DCs are essential for vaccine efficacy.…”

“…CD4 1 or CD8 1 T cells were depleted by injection of anti-CD4 antibodies (GK1.5; 125 mg per mouse), or anti-CD8 antibodies (2.43; 250 mg per mouse), respectively, administered 5, 12, and 19 days after vaccination; depletion methods were sufficient to maintain .95% depletion for GK1.5 and .90% for 2.43 over the course of the experiment (supplemental Figure 1, available on the Blood Web site). Anti-CD25 (clone PC61) was used to deplete Tregs, resulting in .95% reduction of CD4 1 CD25 1 cells (supplemental Figure 2 43,44 In some experiments, 3 doses of 3 mg of cytarabine (Pfizer, Auckland, New Zealand) were administered 10 hours apart the day after leukemia challenge.…”