Heterogeneous expression of Toll-like receptors genes in lymphoid tissues of different ages pigs

Toll-like receptors (TLRs), known as the pathogen recognition receptors, recognize the microbial components. The details expression kinetics of TLRs may help to understand the immune responsiveness of pigs, but the expression patterns of all TLRs (TLR1-10) have not yet been studied in pigs. Therefore, this study unravels the expression patterns of the TLR family set of genes (TLR1-10) in different lymphoid tissues collected from pigs at different ages. A total of nine clinically healthy Pietrain pigs at three age groups were selected for this experiment. Each age group consisted of three animals. Cervical lymph node (CLN), thymus, liver, spleen, lung, heart, skin tissue and peripheral blood mononuclear cells (PBMC) were collected for both mRNA and protein isolation. The mRNA expression of TLRs (1-10) was quantified in all tissues. TLR3 mRNA was the most abundant in all tissues. It was expressed highly in thymus, kidney, lungs and liver tissues. Western blot and immunofluorescence was performed for protein expression and localization of selected TLRs (TLR2, 3 and 9) in selected tissues (CLN, spleen and lungs). The Western blot results of TLR2, 3 and 9 in selected tissues appeared to be consistent with the mRNA expression results. Cells in lungs, spleen and CLN were positively immunostained for TLR2, 3 and 9. This study sheds light on the expression patterns of TLR (1-10) genes in important lymphoid tissues in pigs of different ages. The heterogeneous expression of TLRs with ages may contribute to the altered immune responsiveness of pigs with ages.