Porcine toll-like receptors and their crosstalk with immunobiotics: Impact in the regulation of gut inflammatory immunity

Intestinal epithelial cells (IECs) and immune cells express a range of pattern recognition receptors (PRRs) that are specialized to recognize microbe-associated molecular patterns (MAMPs) present in microbials. The best characterized are the Toll-like receptors (TLRs), which play a key role in pathogen recognition and the induction of innate effectors and inflammation. Moreover, recent findings suggest that TLRs are important in intestinal homeostasis and appear to play a role in tolerance to foreign antigens and commensal bacteria as well as in the immunomodulatory effect of immunobiotics within probiotics. In recent years, there has been a growing interest in the swine immune system because of the economic importance of swine as livestock and also its possible use as a model for the human immune system. In this review article, we summarized our recent research on the immunoregulatory effects of immunobiotic lactic acid bacteria (LAB) via porcine TLRs. We described the development of molecular immunoassay systems that allow the selection of immunobiotic LAB and immunostimulatory DNA sequences from immunobiotics via porcine TLR signaling. In addition, we described the development of in vitro systems using a clonal porcine intestinal epitheliocyte cell line (PIE cells), which could be a useful tool for the study of TLR activation on IECs for the selection of immunobiotic LAB strains with specific immunoregulatory properties and for studying the certain mechanisms of immunobiotic action.