Important Role of Polymeric Immunoglobulin Receptor in Mucosal Immunity

Polymeric immunoglobulin receptor(pIgR)is a kind of type Ⅰ trans-membrane glycoprotein,which could transport via transcytosis from the basal membrane to the apical membrane of epithelia by specifically binding to polymeric IgA or polymeric IgM.At last,the complex of pIgR-polymeric IgA or pIgR-polymeric IgM is released into the secretion as sIgA or sIgM.During this process,the extracellular domain of pIgR is cleaved and released as secretory component(SC)together with polymeric IgA or polymeric IgM.SC is not only the important component of sIgA which directly participate in the mucosal protect function of sIgA,but also plays an important role in the passive mucosal immunity.pIgR can mediate the transcytosis of polymeric IgA,and thus ensures the multiple functions of sIgA,such as luminal prevention of pathogen attachment,intracellular neutralization of viruse and secretion of antigen from lamina propria.Thus,the efficient secretion of pIgR is a prerequisite of polymeric IgA-mediated mucosal protection.However,it seems that pIgR sometimes permits pathogens to invade the epithelial barrier.pIgR is highly N-glycosylated,the unique glycans,which may play a role in the transcytosis of this receptor.Furthermore,these glycans may insure the correct localization of sIgA on mucosa or facilitate the adhering of antigen to epithelial cells.The involvement of multiple molecular mechanisms indicates the influential roles of pIgR and SC im mucosal immunity.