Selective suicide of cross-presenting CD8 ⁺ dendritic cells by cytochrome c injection shows functional heterogeneity within this subset

Abstract

Cross-presentation as a fundamental pathway of activating CD8 ؉ T cells has been well established. So far the application of this concept in vivo is limited, and the mechanisms that specialize CD8 ؉ dendritic cells (DCs) for this task are not fully understood. Here we take advantage of the specific cytosolic export feature of crosspresenting DCs together with the property of cytosolic cytochrome c (cyt c) in initiating Apaf-1-dependent apoptosis selectively in cross-presenting DCs. A single i.v. injection of cyt c in B6 mice produced a 2-to 3-fold reduction in splenic CD8 ؉ DCs but not in Apaf-1-deficient mice. Functional studies both in vivo and in vitro showed that cyt c profoundly abrogated OVA-specific CD8 ؉ T cell proliferation through its apoptosis-inducing effect on crosspresenting DCs. More importantly, in vivo injection of cyt c abolished the induction of cytotoxic T lymphocytes to exogenous antigen and reduced subsequent immunity to tumor challenge. In addition, only a proportion of CD8 ؉ DCs that express abundant IL-12 and Toll-like receptor 3 were efficient cross-presenters. Our data support the hypothesis that cross-presentation in vivo requires cytosolic diversion of endocytosed proteins, conferring cross-presentation specialization to a proportion of CD8 ؉ DCs. We propose that DCs incapable of such transfer, even within the CD8 ؉ DC subset, are unable to cross-present. Our model opens an avenue to specifically target cross-presenting DCs in vivo for manipulating cytotoxic T lymphocyte responses toward infections, tumors, and transplants.antigen presentation ͉ apoptosome ͉ cytotoxic T cells

GM‐CSF increases cross‐presentation and CD103 expression by mouse CD8+ spleen dendritic cells

“…GM-CSF also selectively regulates CD103 on resident CD8 1 DC expression: infectioninduced GM-CSF hyperexpression (as well as transgenic hyperexpression) drives this CD103 upregulation and the GM-CSF receptor is required for this upregulation. CD103 expression provides further functional division within CD8 1 DCs and this supports our previous contention that not all CD8 1 DCs crosspresent efficiently [19].It has been reported previously that GM-CSF in vitro does not grossly influence the expression of costimulatory molecules on CD8 1 DCs [20]. We found here that overexpression of GM-CSF in vivo also does not enhance the expression of CD80 and CD86 or MHC class II expression.…”

In vivo depletion of DC impairs the anti‐tumor effect of agonistic anti‐CD137 mAb

“…DC are considered the principal cross-presenting cells [19,40,41]. In our hands TDLN B cells and macrophages do not crosspresent OVA to sensitive OT-I CD8 1 T cells.…”

“…Zinkernagel's group has challenged this view proposing that CTL priming is critically dependent on tumor cells reaching lymphoid tissue [17]. ''Peaceful'' coexistence between DC cross-priming and direct presentation is taking place in our model as proposed previously [21], although the involvement of BM-derived cells seems to predominate.DC are considered the principal cross-presenting cells [19,40,41]. In our hands TDLN B cells and macrophages do not crosspresent OVA to sensitive OT-I CD8 1 T cells.…”

“…APC have the ability to take up cell-associated antigens and present them in the context of MHC class I molecules to CD8 1 T cells in a process referred to as crosspresentation [40]. A series of reports have indicated that crosspriming is a specific property of DC [19,40,41]. Here, we sought to investigate the involvement of DC in tumor antigen crosspresentation in the EG7-OVA tumor model.…”

“…5B). Importantly, the CD8a 1 DC, whose function in cross-priming has been established [41], expressed the transgenes (Fig. 5A) and became depleted (data not shown).…”