Expression of Siglec-1, -3, -5 and -10 in porcine cDC1 and cDC2 subsets from blood, spleen and lymph nodes and functional capabilities of these cells.

Dendritic cells are professional antigen-presenting cells that play a critical role in the development of immune responses. DCs express a variety of Siglecs on their surface, which play a regulatory role modulating their activation through interaction with sialylated structures expressed by cells or pathogens. Here, we characterized the phenotype of porcine conventional dendritic cells subsets from blood, spleen and lymph nodes, emphasizing the analysis of the expression of Siglecs. Siglec-1 was detected in type 1 cDC and, at lower levels, in type 2 cDC in the spleen, being low to negative in blood and lymph node cDC. Siglec-3 and Siglec-5 were expressed in cDC1 at lower levels than in cDC2. Porcine cDCs did not express Siglec-10. cDC2 showed a higher capacity to phagocytose microspheres and to process DQ™-OVA than cDC1, but none of these functions was affected by engagement of Siglec-3 and -5 with antibodies on blood cDC.

Expression of TLR4 in swine as assessed by a newly developed monoclonal antibody.

Toll-like receptors (TLRs) constitute an ancient family of pattern recognition receptors for conserved microbial structures that allow rapid detection of invading pathogens, triggering immune responses. TLR4 binds lipopolysaccharides (LPS) being involved in the recognition of Gram-negative bacteria. Herein we describe the generation and characterisation of a monoclonal antibody, named 3H3, against porcine TLR4. Its specificity was confirmed by reactivity with TLR4 expressing CHO cell transfectants. On peripheral blood leukocytes TLR4 was preferentially expressed on myelomonocytic cells, with monocytes expressing higher levels than granulocytes. Staining of lung tissue sections showed that TLR4 is also expressed on epithelial cells lining the bronchial tract, a distribution consistent with a surveillance function of bacterial invasion.