Developmental expression patterns and correlation analysis of TLR4 and its downstream genes in the intestinal and immune tissues of Meishan pigs

ABSTRACT To understand the developmental expression patterns of key genes in the Toll-like receptor 4 ( TLR4 ) pathway and their regulatory characteristics in the immune response in pigs, we examined TLR4 and its downstream genes expression levels in the intestinal and immune tissues of Meishan pigs. The genes were expressed in all examined tissues at the different developmental stages. TLR4 expression was higher in spleen and lower in other tissues. Spleen and lymph TLR4 expression was significantly lower in 7- and 35-day-old pigs; in the intestinal tissues, it was significantly lower in 21- and 35-day-old pigs. IFNA, IL1B , and TNFA expression varied greatly with developmental stage; expression was significantly higher in most tissues in 21-, 134-, and 158-day-old pigs. TLR4 was highly positively correlated with TNFA in the immune tissues and was significantly correlated with all downstream genes in the spleen; there was no significant correlation in the intestinal tissues. There was near significant positive correlation among the downstream genes in the intestinal tissues, but almost no significant correlation in the immune tissues. We speculated that the TLR4 pathway genes may have an anti-lipopolysaccharide invasion effect during weaning, and the high expression of the downstream genes is beneficial for improving immunity in adult pigs. Our results may contribute to better understanding the TLR4 signaling pathway and its molecular mechanisms and could provide a reference and basis for appropriate-age experimental animal selection for relevant future research.