PIGR (F9A8F) Rabbit mAb #59629

Polymeric immunoglobulin receptor (PIGR) is a highly glycosylated type I membrane protein that mediates transcytosis of immunoglobulin A (IgA) and immunoglobulin M (IgM) across epithelial cells at mucosal surfaces (1,2). The extracellular portion of PIGR is made up of six domains. Domains 1 through 5 are composed of Ig-like domains that bind to IgA dimers or IgM pentamers, and domain 6 contains a conserved proteolytic cleavage site (3). PIGR binds Ig made in the lamina propria via the joining (J) chain. It undergoes clathrin-mediated endocytosis and is further transcytosis through the epithelial cell to the mucosa (4). PIGR then undergoes endoproteolytic cleavage and disassociates from the membrane domain to form the secretory component (SC) and associated Ig, or secretory Ig (SIg) (5). SC enhances SIg stability by resisting proteolytic degradation and can act as a non-specific microbial scavenger, leading to the sequestration of bacteria in the mucus layer (6,7). PIGR expression and SIg secretion are induced by microbial factors, including LPS, butyrate, and dsRNA, and by pro-inflammatory cytokines like IFN-γ, TNF-α, IL-1, and IL-17 (8). PIGR is expressed aberrantly in cancers and has been proposed as a biomarker with prognostic value and as a therapeutic target (9-11).