Sustained antigen presentation can promote an immunogenic T cell response, like dendritic cell activation

Abstract

Activation of dendritic cells (DCs) enhances their ability to prime naïve T cells. How activation renders them immunogenic rather than tolerogenic is unclear. Here, we show, using temporally regulated expression of a transgene-encoded neoself antigen in DCs, that either prolonged antigen presentation or DC activation could elicit full expansion, effector cytokine production, and memory-cell differentiation. Microarray analysis of gene expression in T cells showed that all changes linked to DC activation through CD40 could be reproduced by persistent antigen delivery, suggesting that stabilization of antigen presentation is an important consequence of DC activation in vivo. In this system, DC activation by CD40 engagement indeed extended their ability to present antigen to CD4 ؉ T cells in vivo, although different results were obtained with antigen delivered to DCs by means of endocytosis from the cell surface. These results suggest that antigen persistence may be an important discriminator of immunogenic and tolerogenic antigen exposure.immune response ͉ immune tolerance ͉ regulated transgene ͉ MHC class II T he interaction of naïve T cells with antigen-presenting DCs is crucial for the initiation of T cell-dependent immune responses but can also result in T cell deletion, anergy, or diversion to a regulatory cell phenotype. Numerous in vitro studies have demonstrated that activation of DCs leads to more effective T cell priming, whereas presentation by immature DCs elicits abortive activation or anergy. After activation, DCs undergo a number of phenotypic changes that may explain their stronger stimulatory capacity: increased MHC protein expression, up-regulation of adhesion and costimulatory molecules, and induction of chemo-and cytokine secretion. The relative role of these components for T cell responses, however, remain unclear (1-4).The importance of sustained signaling via the T cell receptor (TCR) for T cell commitment to expansion and effector gene expression was first shown in vitro, by using tumor cells, T cell lines, and TCR-transgenic T cells (5-7). Iezzi et al. (8) proposed that the duration of antigen presentation is ''the major factor'' determining T cell behavior. Using an approach wherein antigen presentation to CD4 ϩ T cells can be controlled by a transgenic switch in vivo, we have recently shown that antigen persistence tightly controls the expansion of CD4 ϩ T cells. Our studies showed, unexpectedly, that presentation of a neoself antigen is effective in the absence of DC activation, if persistent. We now ask whether DC activation modifies these parameters. Previous in vitro experiments revealed that MHC class II molecules are stabilized at the cell surface of DCs upon activation, a phenomenon summarily referred to as ''antigenic memory'' (9-11) and recently found to be regulated by ubiquitination (12-14). By examining the genomic signature of T cells triggered by antigen presented by resting or activated forms of DCs, we find that the programmatic differences elicited in T cells by DC acti...

Intradermal immunization in the ear with cholera toxin and its non‐toxic β subunit promotes efficient Th1 and Th17 differentiation dependent on migrating DCs

“…Despite robust T-cell proliferation, only minimal IL-2 expression and no production of IFN-g and IL-17 in HEL-re-stimulated CD4 1 T cells was observed in mice in which the immunization site was removed 90 min after immunization with HEL and either CT or CTB. Consistent with previous reports [32], this result suggests that in our model, sustained antigen presentation (in this case, mediated by DCs that migrate from the ear and arrive at dCLNs) is crucial for inducing CD4 1 T cells to differentiate into cytokineproducing cells, even in the presence of strong adjuvants such as CT. Our experiments indicate that migrating cells that arrive after 90 min but within the first 24 h of immunization are important for T-cell differentiation. Considering the migration kinetics of skin DCs, even in the presence of adjuvants [6,7], it is very possible that in our model, dermal DCs achieve initial antigen presentation and priming, which is consistent with previous reports [12,13].…”

Differential Kinetics of Antigen Dependency of CD4+ and CD8+ T Cells

“…7 shows that AND but not OT1 T cells detected remaining pMHC complexes. We have shown previously that this proliferation of AND T cells was not caused by increased costimulation (42). These findings indicate that the turnover of K b /Ova 257-264 complexes is not affected by DC maturation in such a way that OT1 cells might detect them 3 d after dox turn-off.…”

“…In view of our finding that CD4 + and CD8 + T cells differ in their temporal requirements of TCR signals, we asked whether the kinetics of Ag presentation differs for their respective MHC ligands on DCs, the main APCs for priming. Because MHC class II molecules are stabilized on the cell surface upon DC activation by downregulated oligo-ubiquitination of class II b-chains (59, 60) by membrane-associated RING-CHlike E3 ligases (61,62) in vitro (63,64) and in vivo (42,65), we tested whether DC activation affects molecules of both MHC classes similarly. We activated dtg-M and -O DCs in vivo by treatment with a stimulatory CD40 mAb and fed the animals with dox for 24 h subsequently.…”

“…For Th1 and Th2 differentiation of AND T cells in vitro, cells were stimulated with anti-CD3 and anti-CD28 in complete medium containing 5 ng/ml IL-12 and 20 mg/ml anti-IL-4 mAb (11B11) for Th1 conditioning or 50 ng/ml IL-4 and 50 mg/ml anti-IFN-g mAb (XMG1.2; both BioXCell) for Th2 conditioning. Following stimulation, cells were CFDA-SE labeled and transferred as described previously (42).…”

“…Transferred CD4 + or CD8 + T cells were stained and CD4 + /CD8 + CD45.1 + DAPI 2 cells were sorted twice, the second time with a purity of 99-100% directly into TRIzol (Invitrogen). RNA from sorted cells was isolated as described previously (42). One to 20 ng high-quality total RNA (RNA integrity number.…”