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

Abstract

Within the ruminant system, several possibilities exist to generate dendritic cells migrating out from the tissue into the regional draining lymph nodes as afferent lymph dendritic cells (ALDCs). Here, we analyzed toll-like receptor (TLR) 1-10 mRNA expression by using quantitative real-time PCR in highly purified subsets of bovine ALDC. As TLR expression may be influenced by pathogens or vaccines and their adjuvant, it is necessary to understand what TLRs are expressed in a steady-state system to elucidate specific differences and to potentially optimize targeted vaccines. In this study, we have assessed the TLR expression profiles of the four main bovine ALDC subsets [cDC1 and cDC2 (subsets 2-4)]. We demonstrate differences in TLR expression between the four subsets that may reflect the ability of these cells to respond to different pathogens or to respond to adjuvants.

Keywords: afferent lymph; bovine; dendritic cell; dendritic cell subsets; toll-like receptors.

Figure 1

Expression of toll-like receptors (TLRs) by the subsets of dendritic cells (DC) in bovine afferent lymph. Subsets of afferent lymph dendritic cells (ALDCs), as used in this study (see Presentation S2 in Supplementary Material), were analyzed by real-time PCR for their comparative expression of the 10 bovine TLRs. Expression of each TLR was normalized to the expression level of the housekeeping gene representing the large fragment of the RNA polymerase (RPLPO). Differences in expression between the ALDC subsets were assessed by repeated measures two-way analysis of variance followed by Bonferroni t-tests. Significant differences in expression were detected for TLR1, TLR2, TLR4, TLR7, and TLR10. Asterisks denote significant differences in mRNA expression of a given TLR between subsets: ***p value <0.001, **p value <0.01, *p value <0.05.