Background/Purpose:

Tolerogenic dendritic cells (tDCs) are a promising therapeutic tool for specific induction of immunological tolerance. Human tDCs can be generated ex vivo using various compounds. However, the compound(s) most suitable for clinical application remain undefined. For clinical application of tDCs, three functional characteristics are required: 1) CCR7-dependent migration toward secondary lymphoid organs; 2) efficient induction of functional regulatory T cells; and 3) stability upon exposure to proinflammatory stimuli. We found that DCs (PKCI-tDCs) treated with protein kinase C inhibitor (PKCI) had potent tolerogenic properties. Since aberrant activation of T cells, especially CD4⁺ T cells, plays an important role in the initiation and/or perpetuation of rheumatoid arthritis (RA) and primary Sjögren’s syndrome (pSS), both diseases may be suitable for tolerance-inducing therapy. In this study, we described the characterization of PKCI-tDCs and examined whether PKCI-tDCs could be generated from patients with RA or pSS.

Methods:

1) Generation of human tDCs: Immature DCs (iDCs) were generated from the monocytes by culturing them in X-VIVO medium with GM-CSF and IL-4 for 5 days. To induce mature DCs (mDCs), iDCs were incubated with a maturation cocktail for a further 48 h. Compound-treated tDCs were generated by culturing iDCs with a maturation cocktail in the presence of each compound for 48 h. 2) Other methods: In vitro T cell proliferation assay; cytokine production; phagocytic ability; induction of regulatory T cells; in vitro T regulatory activity; stability of DCs under proinflammatory stimuli; and chemotaxis assay.

Results:

PKCI-tDCs had a semi-mature phenotype, showing high production of IL-10, and efficiently induced IL-10-producing T cells and functional Foxp3⁺ regulatory T cells, thus eliciting a strong immunosuppressive function. They also showed CCR7 expression and sufficient capacity for migration toward CCR7 ligands. In addition, PKCI-tDCs were highly stable when exposed to inflammatory stimuli. PKCI inhibited NF-kB activation of both the canonical and non-canonical pathways of DC maturation, thus suppressing the expression of costimulatory molecules and IL-12 production. High production of IL-10 in PKCI-tDCs was due to not only an increase of intracellular cAMP, but also a synergistic effect of increased cAMP and NF-kB inhibition. PKCI-treated DCs from the patients with RA or pSS had similar phenotypes and suppressive properties to those from healthy donors.

Conclusion:

PKCI-tDCs may be useful for tolerance-inducing therapy, since they satisfy the required functional characteristics for clinical-grade tDCs. In addition, PKCI-tDCs were generated from patients with RA or pSS not only before but also after treatment with agents such as methotrexate and prednisolone.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/characterization-of-human-tolerogenic-dendritic-cells-generated-with-protein-kinase-c-inhibitor-and-induction-from-patients-with-autoimmune-diseases/