Dendritic Cell Activating Receptor 1 (DCAR1) Associates With FcεRIγ and Is Expressed by Myeloid Cell Subsets in the Rat

Abstract

Dendritic cell activating receptor-1 (DCAR1) is a cell-surface receptor encoded by the Antigen Presenting Lectin-like gene Complex (APLEC). We generated a mouse monoclonal antibody against rat DCAR1, and used this to characterize receptor expression and function. Rat DCAR1 was expressed on minor subsets of myeloid cells in lymphoid tissue, but was uniformly expressed at a high level by eosinophils, and at a low level by neutrophils. It was expressed by eosinophils in the peritoneal cavity and the lamina propria of the gut, and by subsets of macrophages or dendritic cells at these sites. Polarization of peritoneal macrophages showed that DCAR1 expression was absent on M1 macrophages, and increased on M2 macrophages. DCAR1 could be expressed as a homodimer and its associated with the activating adaptor protein FcεRIγ. This association allowed efficient phagocytosis of antibody-coated beads. Additionally, cross-linking of DCAR1 on the surface of rat eosinophils lead to production of reactive oxygen species. These data show that DCAR1 is an activating receptor. Its expression on M2 macrophages and eosinophils suggests that it may play a role in the immune response to parasites.

Identification of Clec4b as a novel regulator of bystander activation of auto-reactive T cells and autoimmune disease

“…The production of a monoclonal antibody for rat Clec4b is described in recently published data from Daws et al [18]. They also detailed how Clec4b is expressed mainly on CD4 + DC/monocytes [18]. We found that Clec4b was only expressed in Clec4b E3 CD4 + DCs but not in B or T cells ( Fig 3F).…”

“…Lower levels of Clec4b were observed in pDCs, albeit without any strain difference ( Fig 2D). A recent study by Daws et al [18] supports both of these findings, suggesting that rat Clec4b is highly expressed in CD4 + myeloid cells but not in CD4 + pDCs.…”

“…Since the pDC population was shown to express very low levels of Clec4b (see Fig 2D), we conclude that the CD11b/c + DC population should be the main Clec4b expressing CD4 + population in the spleen. The production of a monoclonal antibody for rat Clec4b is described in recently published data from Daws et al [18]. They also detailed how Clec4b is expressed mainly on CD4 + DC/monocytes [18].…”

Glycan Activation of Clec4b Induces Reactive Oxygen Species Protecting against Neutrophilia and Arthritis

“…Fluorescently activated cell sorted splenic neutrophils ( Figure 2 B) were found to express readily Clec4b at a steady-state level. Using a rat Clec4b specific monoclonal antibody (clone: Wen41) [ 28 ], we confirmed by flow cytometry the protein expression on neutrophils ( Figure 2 C). We have earlier shown that the expression of Clec4b on CD4+ dendritic cells are regulating the activation of autoreactive T cells [ 23 ] but since the strongest expression is on neutrophils that play an important role in the development of arthritis [ 29 , 30 ], we now suggest an additional Clec4b-mediated neutrophil function.…”

Rat cytomegalovirus-encoded γ-chemokine vXCL1 is a highly adapted, species-specific agonist for rat XCR1-positive dendritic cells

“…Endogenous (host) XCL1 is secreted predominantly by natural killer (NK) cells in the early innate response as well as by CD8 + T cells in the adaptive phase, and it induces chemotaxis only in XCR1expressing dendritic cells (DCs) that are likely to represent conventional dendritic cells 1 (cDC1; Daws et al, 2019;Guilliams et al, 2014;Voisine et al, 2002). XCR1 is predominantly co-expressed on CD8a + mouse cDC1, CD141 + human cDC1 and CD4 − rat DCs, and has been suggested as a lineage marker to phenotype antigen crosspresenting DCs since XCR1 + DCs are involved in the induction of cytotoxic CD8 + T cell responses (Crozat et al, 2010;Gurka et al, 2015;Kroczek and Henn, 2012).…”