Tolerogenic dendritic cells (tolDCs) are a promising treatment modality for diseases caused by a breach in immune tolerance, such as rheumatoid arthritis. Current medication for these diseases is directed toward symptom suppression but no real cure is available yet. TolDC-based therapy aims to restore immune tolerance in an antigen-specific manner. Here we used a mouse model to address two major questions: (i) is a maturation stimulus needed for tolDC function in vitro and in vivo and is maturation required for functioning in experimental arthritis and (ii) can tolDCs modulate CD4+ T cell responses? To answer these questions, we compared matured and immature dexamethasone/vitamin D3-generated tolDCs in vitro. Subsequently, we co-transferred these tolDCs with naïve or effector CD4+ T cells to study the characteristics of transferred T cells after 3 days with flow cytometry and Luminex multiplex assays. In addition, we tested the suppressive capabilities of tolDCs in an experimental arthritis model. We found that tolDCs cannot only modulate naïve CD4+ T cell responses as shown by fewer proliferated and activated CD4+ T cells in vivo, but also effector CD4+ T cells. In addition, Treg (CD4+CD25+FoxP3+) expansions were seen in the proliferating cell population in the presence of tolDCs. Furthermore, we show that administered tolDCs are capable to inhibit arthritis in the proteoglycan-induced arthritis model. However, a maturation stimulus is needed for tolDCs to manifest this tolerizing function in an inflammatory environment. Our data will be instrumental for optimization of future tolDC therapies for autoimmune diseases.

Tolerogenic dendritic cells (DCs) can induce regulatory T cells and dampen pathogenic T cell responses. Therefore, they are possible therapeutic targets in autoimmune diseases. In this study we investigated whether mouse tolerogenic DCs are induced by the phytonutrient carvacrol, a molecule with known anti-inflammatory properties, in combination with a physiological stress. We show that treatment of DCs with carvacrol and thermal stress led to the mRNA expression of both pro- and anti-inflammatory mediators. Interestingly, treated DCs with this mixed gene expression profile had a reduced ability to activate pro-inflammatory T cells. Furthermore, these DCs increased the proportion of FoxP3(+) regulatory T cells. In vivo, prophylactic injection of carvacrol-thermal stress treated DCs pulsed with the disease inducing antigen was able to suppress disease in a mouse model of arthritis. These findings suggest that treatment of mouse bone marrow derived DCs with carvacrol and thermal stress induce a functionally tolerogenic DC that can suppress autoimmune arthritis. Herewith carvacrol seems to offer novel opportunities for the development of a dietary based intervention in chronic inflammatory diseases.

Autologous tolerogenic dendritic cells (tolDC) are a promising therapeutic strategy for inflammatory arthritis (IA) as they can regulate autoantigen-specific T cell responses. Here, we investigated two outstanding priorities for clinical development: (i) the suitability of using heat-shock proteins (HSP), abundant in inflamed synovia, as surrogate autoantigens to be presented by tolDC and (ii) identification of functional biomarkers that confirm tolDC regulatory activity.

Cellular therapies with tolerogenic antigen-presenting cells (tolAPC) show great promise for the treatment of autoimmune diseases and for the prevention of destructive immune responses after transplantation. The methodologies for generating tolAPC vary greatly between different laboratories, making it difficult to compare data from different studies; thus constituting a major hurdle for the development of standardised tolAPC therapeutic products. Here we describe an initiative by members of the tolAPC field to generate a minimum information model for tolAPC (MITAP), providing a reporting framework that will make differences and similarities between tolAPC products transparent. In this way, MITAP constitutes a first but important step towards the production of standardised and reproducible tolAPC for clinical application.

Tissue-specific distribution of gammadelta TCRs with limited TCR diversity is a common phenomenon in species with a low percentage of gammadelta T cells like humans and mice. We set out to investigate whether this is also the case in cattle (Bos taurus), a species with high percentages of gammadelta T cells. Using a method that was independent of variable (V) segment-specific primers, we generated 65 unique TCR delta chain sequences. We found no evidence for preferential use of certain Vdelta segments in lymph node, skin, spleen, small intestine, large intestine, and blood. The delta chain CDR3 length distribution was very wide in each tissue, which was confirmed by spectratyping. The highly variable CDR3 length was due to the use of up to four diversity (D) segments by one bovine delta chain. Human and murine delta chains contain only one or two D segments. The five functional Ddelta segments that we describe here were identified at cDNA and genomic level, and are the first ruminant D segments described. Fourteen TCR delta chain sequences used novel Vdelta1 segments, and one expressed a novel member of the Vdelta3 family. The number of known functional Vdelta segments in cattle including these new ones is 42 now, but the total number may be much higher. A high number of Vdelta segments in combination with the use of up to four out of five D segments, and the possibility of using non-template encoded (N) nucleotides on either side of these, makes the potential bovine delta chain repertoire much bigger than any known TCR chain. This situation is quite different from the situation in humans and mice, and suggests that the differences between gammadelta high and gammadelta low species in distribution, diversity, and function of gammadelta T cells may be substantial.