Research Progress on the Polymeric Immunoglobulin Receptor (pIgR) in Fish

Abstract

There are a large number of pathogens in the water where fish live, and the mucosal-associated lymphoid tissues (MALTs), such as skin, gill and intestine, are the first contact parts when pathogens infect fish. The secreted mucus of these tissues constitutes the first barrier for fish against the invasion of external pathogens. Mucosal immunity can identify and neutralize pathogens and induces immunocytes to devour pathogens and the like. As a key factor in the mucosal immune system, the polymeric immunoglobulin receptor (pIgR) is capable of mediating the transport and secretion of polymeric immunoglobulins towards mucus. The effective secretion of the pIgR is necessary for polymeric immunoglobulins (pIg) to exert mucosal defence and plays a significant role in fish immunity. With the deepening of research into fish immunoglobulins, the pIgR has become a research hotspot. The molecular structure, genetic structure and expression pattern of the pIgR and the important role it plays in mucosal immunity were summarized in this study, which contributed to a deeper understanding of fish mucosal immunity and laid a foundation for further exploration of the action mechanism and functions of the pIgR in fish.