The second cluster includes 12 genes up-regulated at t=+4 and related to connective tissue disorders and inflammatory diseases (GYG1, PDXK, RETN, C3, IL27, TLR4, IL1RN, ICAM1, CXCL13, C3AR1, FAS, SOD2, and TLR4). Toll-like receptor 4 (TLR4) is essential for initiating the innate response to lipopolysaccharide from Gram-negative bacteria by acting as a signal-transducing receptor. As the pig industry faces a unique array of related pathogens, it is anticipated that the genotype of swine TLR4 could be of crucial importance in future strategies aimed at improving genetic resistance to infectious diseases .