Conventional dendritic cells (cDCs) are divided into the following different subtypes: cDC1, which promotes a Th1 response, and cDC2, which stimulates a Th2 and Th17 response. These cells have not been characterized in porcine lymphoid tissues. DEC205 is a receptor that increases antigen presentation and allows DCs to cross-present antigens. The objectives of this work were to characterize cDCs subsets in the tonsil, submaxillary and mesenteric lymph nodes and spleen lymphoid tissues and to determine their expression of DEC205 by flow cytometry. The cDC1 (MHCIICADM1CD172a) and cDC2 (MHCIICADM1CD172a) phenotypes were confirmed by the expression of characteristic cDC1 and cDC2 transcripts (FLT3, XCR1 and FCER1α). Among all lymphoid tissues, the spleen had the highest frequency of total cDCs. The cDC1:cDC2 ratio showed that all lymph tissues had higher levels of cDC1 than levels of cDC2. DEC205 cDCs were found in all analyzed tissues, albeit with different frequencies. Our research will facilitate the study on the function of these cells and the investigation of the strategies for DEC205 targeting and functional studies.
Conventional dendritic cells (cDCs) cannot be infected by porcine reproductive and respiratory syndrome virus (PRRSV) but respond to infection via cytokine production, indicating a possible role in initiation/regulation of the immune response against PRRSV. In this work, we evaluated the responses of splenic and blood cDCs, with DEC205+CADM1+CD172a+/− phenotype, as well as those of CD163+ cells against PRRSV and porcine epidemic diarrhea virus (PEDV). Both populations were incubated in the presence of PRRSV or PEDV with and without naïve CD3+ T cells, and cytokine responses were evaluated by qPCR and ELISA. Our results showed that cDCs, but not CD163+ cells, produced IL-12 in response to PRRSV. PEDV did not induce IL-12 production. Cocultures of cDCs and autologous naïve CD3+ cells resulted in decreased IL-12 production and low expression of IFN-γ transcripts in response to PRRSV. Interestingly, cDCs increased the proliferation of naïve T cells in the presence of PRRSV compared with that achieved with monocytes and peripheral blood mononuclear cells (PBMCs). Cocultures of CD163+ cells induced IL-10 and IL-4 expression in the presence of PRRSV and PEDV, respectively. In conclusion, cDCs can selectively produce IL-12 in response to PRRSV but poorly participate in the activation of naïve T cells.
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