Characterization and Transcriptomic Analysis of Porcine Blood Conventional and Plasmacytoid Dendritic Cells Reveals Striking Species-Specific Differences

Abstract

Porcine dendritic cells (DCs) are relatively well characterized, but a clear-cut identification of all DC subsets combined with full transcriptional profiling was lacking, preventing an unbiased insight into the functional specializations of DC subsets. Using a large panel of Abs in multicolor flow cytometry, cell sorting, and RNA sequencing we identified and characterized the porcine equivalent of conventional DCs (cDC) 1 and cDC2 as well as plasmacytoid DCs (pDCs) in the peripheral blood of pigs. We demonstrate that cDC1 are CD135CD14CD172aCADM1wCD11R1 cells, cDC2 are CD135CD14CD172aCADM1CD115wCD11R1CD1 cells and pDCs are CD4CD135CD172aCD123CD303 cells. As described in other species, only cDC1 express BATF3 and XCR1, cDC2 express FCER1A and FCGR2B, and only pDCs express TCF4 and NRP1 Nevertheless, despite these cross-species conserved subset-specific transcripts, porcine pDCs differed from the species described so far in many expressed genes and transcriptomic profiling clustered pDCs more distantly from cDCs than monocytes. The response of porcine DC subsets to TLR ligands revealed that pDCs are by far the most important source of TNF-α, IL-12p40, and of course IFN-α, whereas cDCs are most efficient in MHC and costimulatory molecule expression. Nevertheless, upregulation of CD40 and CD86 in cDCs was critically influenced or even dependent on the presence of pDCs, particularly for TLR 7 and 9 ligands. Our data demonstrate that extrapolation of data on DC biology from one species to another has to be done with care, and it shows how functional details have evolved differentially in different species.

Characterization and expression of DEC205 in the cDC1 and cDC2 subsets of porcine dendritic cells from spleen, tonsil, and submaxillary and mesenteric lymph nodes

“…To confirm the phenotypes for the cDC1 and cDC2 subtypes, the expression of XCR1 and FCeR1α was evaluated. As previously described (Maisonnasse et al, 2016a;Auray et al, 2016), the cDC1 subtype expressed transcripts for XCR1 and was negative for FCeR1α; in contrast, the cDC2 was XCR1 negative and FCeR1α positive (Fig. 2).…”

“…Maisonnasse et al (2016a,b) described similar results in lung and bronchoalveolar lavage (Maisonnasse et al, 2016a;Maisonnasse et al, 2016b). Auray et al (2016) recently characterized porcine blood cDCs, and classified cDC1 as CD135 + CD172a l°C ADM1 + and cDC2 as CD135 + CD172a + CADM1 + (Auray et al, 2016); meanwhile, Edwards et al (2017) classified cDCs as CD1 − (Lin − CD172a + CD1 − CD4 − ), and CD1 + cDC (Lin − CD172a + CD1 + CD4,) (Edwards et al, 2017). These previous characterizations are fundamental for further studies that use DCs as models for human health research.…”

“…This receptor is also highly expressed on human myeloid CD11c + DCs as well as in monocytes and on T and B lymphocytes (Kato et al, 2006). DEC205 has been characterized in swine (Flores-Mendoza et al, 2010), and a recent study showed that the porcine blood cDC1, cDC2 and pDCs are DEC205 + (Auray et al, 2016). However, there are no studies on the expression of this important receptor on the porcine cDCs subtypes from lymph tissues.…”

Subset-Specific Expression of Toll-Like Receptors by Bovine Afferent Lymph Dendritic Cells

“…These studies suggest that the previously defined CD172a + and CD172a − ALDC represent classical (c)DC1 (CD11a + , CD13 + , CD26 + , CD172a low/− ), and cDC2 subsets (CD11a − , CD13 − , CD26 − , CD172a + ). These subsets are similar, but distinctively different from the recently described porcine cDC1 and cDC2 subsets (12). Within the bovine cDC2 subset, three major subpopulations have been defined: CD172a + CD206 + CD1b ++ CD21 + , CD172a + CD206 − CD1b + CD21 +/− , and CD172a + CD206 − CD1b +/− CD21 − (1, 8, 11, 13, 14).…”

A Universal Influenza Vaccine Can Lead to Disease Exacerbation or Viral Control Depending on Delivery Strategies

“…However in the mouse, both pDC and cDC respond to TLR9 stimulation whereas in human, only pDC express TLR9 (52). A very recent study in pigs show that although cDC and monocyte-derived DC express TLR9 mRNA, they do not upregulate cytokine nor costimulatory molecule expression upon exposure to CpG, unless cocultured with pDC (53, 54). As the skin does not contain pDC at steady state (55), it may explain the low adjuvant effect of CpG given by the ID route.…”