DCIR2+ cDC2 DCs and Zbtb32 Restore CD4+ T-Cell Tolerance and Inhibit Diabetes.

During autoimmunity, the normal ability of dendritic cells (DCs) to induce T-cell tolerance is disrupted; therefore, autoimmune disease therapies based on cell types and molecular pathways that elicit tolerance in the steady state may not be effective. To determine which DC subsets induce tolerance in the context of chronic autoimmunity, we used chimeric antibodies specific for DC inhibitory receptor 2 (DCIR2) or DEC-205 to target self-antigen to CD11b(+) (cDC2) DCs and CD8(+) (cDC1) DCs, respectively, in autoimmune-prone nonobese diabetic (NOD) mice. Antigen presentation by DCIR2(+) DCs but not DEC-205(+) DCs elicited tolerogenic CD4(+) T-cell responses in NOD mice. ß-Cell antigen delivered to DCIR2(+) DCs delayed diabetes induction and induced increased T-cell apoptosis without interferon-γ (IFN-γ) or sustained expansion of autoreactive CD4(+) T cells. These divergent responses were preceded by differential gene expression in T cells early after in vivo stimulation. Zbtb32 was higher in T cells stimulated with DCIR2(+) DCs, and overexpression of Zbtb32 in T cells inhibited diabetes development, T-cell expansion, and IFN-γ production. Therefore, we have identified DCIR2(+) DCs as capable of inducing antigen-specific tolerance in the face of ongoing autoimmunity and have also identified Zbtb32 as a suppressive transcription factor that controls T cell-mediated autoimmunity.

CD8+ dendritic cell-mediated tolerance of autoreactive CD4+ T cells is deficient in NOD mice and can be corrected by blocking CD40L.

DCs are important mediators of peripheral tolerance for the prevention of autoimmunity. Chimeric αDEC-205 antibodies with attached antigens allow in vivo antigen-specific stimulation of T cells by CD8(+) DCs, resulting in tolerance in nonautoimmune mice. However, it is not clear whether DC-mediated tolerance induction occurs in the context of ongoing autoimmunity. We assessed the role of CD8(+) DCs in stimulation of autoreactive CD4(+) T cells in the NOD mouse model of type 1 diabetes. Targeting of antigen to CD8(+) DCs via αDEC-205 led to proliferation and expansion of ß-cell specific BDC2.5 T cells. These T cells also produced IL-2 and IFN-γ and did not up-regulate FoxP3, consistent with an activated rather than tolerant phenotype. Similarly, endogenous BDC peptide-reactive T cells, identified with I-A(g7) tetramers, did not become tolerant after antigen delivery via αDEC-205: no deletion or Treg induction was observed. We observed that CD8(+) DCs from NOD mice expressed higher surface levels of CD40 than CD8(+) DCs from C57BL/6 mice. Blockade of CD40-CD40L interactions reduced the number of BDC2.5 T cells remaining in mice, 10 days after antigen targeting to CD8 DCs, and blocked IFN-γ production by BDC2.5 T cells. These data indicate that the ability of autoreactive CD4(+) T cells to undergo tolerance mediated by CD8(+) DCs is defective in NOD mice and that blocking CD40-CD40L interactions can restore tolerance induction.

CD8 marks a subpopulation of lung-derived dendritic cells with differential responsiveness to viral infection and toll-like receptor stimulation.

An increasing number of studies suggest that individual subsets of dendritic cells (DC) exhibit distinct capabilities with regard to the generation of the adaptive immune response. In this study, we evaluated the properties of a relatively unexplored DC subset present in the lung-draining mediastinal lymph node. This subset expresses the airway dendritic cell marker CD103 together with CD8. These DC were of interest given that our previous studies using a model of respiratory infection with vaccinia virus revealed a distinct difference in the ability of CD103(+) DC to prime T cells that correlated inversely with the expression of CD8, suggesting a differential role of these DC in the context of respiratory virus infection. To expand our understanding of the role of this DC population, we performed analyses to elucidate the phenotype, migratory capacity, responsiveness to innate stimuli, and priming capacity of CD8(+) CD103(+) DC. We found that expression of surface markers on these DC was similar to that of CD8(-) CD103(+) DC, supporting their close relationship. Further, the two DC types were similar with regard to antigen uptake. However, although both CD103(+) subsets originated from the lung, CD8-bearing CD103(+) DC appeared in the lymph node with delayed kinetics following virus infection. While this subset exhibited increased responsiveness to a number of Toll-like receptor (TLR) agonists, their response to infection was virus specific, demonstrating poor responsiveness to vaccinia virus infection but robust maturation following infection with parainfluenza virus 5 or influenza virus. These findings show that CD8 marks a population of lung airway-derived DC with distinct migratory and maturation responses that likely contribute differentially to the immune response depending on the infecting pathogen.

Functional divergence among CD103+ dendritic cell subpopulations following pulmonary poxvirus infection.

A large number of dendritic cell (DC) subsets have now been identified based on the expression of a distinct array of surface markers as well as differences in functional capabilities. More recently, the concept of unique subsets has been extended to the lung, although the functional capabilities of these subsets are only beginning to be explored. Of particular interest are respiratory DCs that express CD103. These cells line the airway and act as sentinels for pathogens that enter the lung, migrating to the draining lymph node, where they add to the already complex array of DC subsets present at this site. Here we assessed the contributions of these individual populations to the generation of a CD8(+) T-cell response following respiratory infection with poxvirus. We found that CD103(+) DCs were the most effective antigen-presenting cells (APC) for naive CD8(+) T-cell activation. Surprisingly, we found no evidence that lymph node-resident or parenchymal DCs could prime virus-specific cells. The increased efficacy of CD103(+) DCs was associated with the increased presence of viral antigen as well as high levels of maturation markers. Within the CD103(+) DCs, we observed a population that expressed CD8alpha. Interestingly, cells bearing CD8alpha were less competent for T-cell activation than their CD8alpha(-) counterparts. These data show that lung-migrating CD103(+) DCs are the major contributors to CD8(+) T-cell activation following poxvirus infection. However, the functional capabilities of cells within this population differ with the expression of CD8, suggesting that CD103(+) cells may be divided further into distinct subsets.