A new assay system for detection of polymeric immunoglobulin A-polymeric immunoglobulin receptor binding

A new system for detection of polymeric immunoglobulin A (pIgA)-polymeric immunoglobulin receptor (pIgR) binding was established. Cell lysates of a mouse pIgR cDNA transfectant, 2S9.1, were incubated with mouse polymeric immunoglobulin A (pIgA) or immunoglobulin G (IgG). The resulting immunocomplexes were precipitated with protein G-Sepharose and blotted with polyclonal anti-mouse pIgR antibody. The mouse pIgR molecule was specifically precipitated with pIgA, indicating successful detection of the pIgA-pIgR complex. Using this system, the role of N-glycosylation in pIgA-pIgR binding was examined. The pIgR molecule (molecular mass 100 kDa) after complete deglycosylation by tunicamycin treatment was still able to bind to pIgA, indicating that N-glycosylation of pIgR is not necessary for pIgA-pIgR binding. This novel system will be useful for detecting pIgA-pIgR complexes containing intact pIgR molecules.