Human CD103⁺dendritic cells promote the differentiation ofPorphyromonas gingivalisheat shock protein peptide-specific regulatory T cells

Abstract

PurposeRegulatory T cells (Tregs), expressing CD4 and CD25 as well as Foxp3, are known to play a pivotal role in immunoregulatory function in autoimmune diseases, cancers, and graft rejection. Dendritic cells (DCs) are considered the major antigen-presenting cells (APCs) for initiating these T-cell immune responses, of which CD103+ DCs are derived from precursor human peripheral blood mononuclear cells (PBMCs). The aim of the present study was to evaluate the capacity of these PBMC-derived CD103+ DCs to promote the differentiation of antigen-specific Tregs.MethodsMonocyte-derived DCs were induced from CD14+ monocytes from the PBMCs of 10 healthy subjects. Once the CD103+ DCs were purified, the cell population was enriched by adding retinoic acid (RA). Peptide numbers 14 and 19 of Porphyromonas gingivalis heat shock protein 60 (HSP60) were synthesized to pulse CD103+ DCs as a tool for presenting the peptide antigens to stimulate CD3+ T cells that were isolated from human PBMC. Exogenous interleukin 2 was added as a coculture supplement. The antigen-specific T-cell lines established were phenotypically identified for their expression of CD4, CD25, or Foxp3.ResultsWhen PBMCs were used as APCs, they demonstrated only a marginal capacity to stimulate peptide-specific Tregs, whereas CD103+ DCs showed a potent antigen presenting capability to promote the peptide-specific Tregs, especially for peptide 14. RA enhanced the conversion of CD103+ DCs, which paralleled the antigen-specific Treg-stimulating effect, though the differences failed to reach statistical significance.ConclusionsWe demonstrated that CD103+ DCs can promote antigen-specific Tregs from naive T cells, when used as APCs for an epitope peptide from P. gingivalis HSP60. RA was an effective reagent that induces mature DCs with the typical phenotypic expression of CD103 that demonstrated the functional capability to promote antigen-specific Tregs.Graphical Abstract

Differential regulation of CD103 (αE integrin) expression in human dendritic cells by retinoic acid and Toll-like receptor ligands

“…As we were (continued on next page) unable to detect a significant amount of intracellular b7 integrin, the intracellular CD103 may correspond to abortive expression of the CD103 monomer. A number of reports have investigated the influence of human DC treatment with RA on the ability of DCs to prime T cells [18,20,36,38]. Overall, human DCs exposed to RA display a more anti-inflammatory phenotype, with increased IL-10 and decreased IL-12 production [36], consistent with our observations of decreased CD83, CD86, and HLA-DR expression and increased ILT3 expression.…”

“…Our data confirm and extend previous reports of CD103 upregulation by RA in human MoDCs [16][17][18]. Importantly, we used an improved culture system with physiologic concentrations of RA (100 nM), as well as a serum-free medium, thereby eliminating confounding effects of retinoids and TGF-b found in human and animal sera.…”

“…In a recent study in human CD8 + T cells, Mokrani et al [15] identified specific bindings sites for Smad2/3, important transcription factors activated by TGF-b, in promoter and enhancer regions of the ITGAE gene, which encodes CD103. However, several independent studies using human DCs derived from blood monocytes or CD34 + progenitor cells did not observe increased CD103 expression with rTGF-b [16][17][18][19] but found increased surface expression of CD103 in response to RA [16][17][18]20].…”

Critical role of CCL22/CCR4 axis in the maintenance of immune homeostasis during apoptotic cell clearance by splenic CD8α+CD103+ dendritic cells

“…CD103 + DCs in several tissues, especially in intestine, lung, pancreas and mesenteric lymph nodes, have been reported to induce peripheral tolerance . Moreover, recent research showed that human peripheral blood mononuclear cell‐derived CD103 + DCs and retinoic‐acid‐primed CD103 + DCs also have the ability to promote the differentiation of Treg cells . Taken together, peripheral CD103 + DCs are the critical regulators of immune homeostasis.…”

“…11,[39][40][41] Moreover, recent research showed that human peripheral blood mononuclear cell-derived CD103 + DCs and retinoic-acid-primed CD103 + DCs also have the ability to promote the differentiation of Treg cells. 42,43 Taken together, peripheral CD103 + DCs are the critical regulators of immune homeostasis. In addition, CCL22 may be used as a candidate to study the molecular mechanisms involved in tolerance induction by peripheral CD103 + DCs.…”