PIGR and bacterial infectious disease: Our group was particularly interested in the role of sIgA in infection, especially bacterial infection, and developed a pIgR knockout mouse (pIgR-/-) in the C57BL/6 (BL/6) background, in collaboration with Per Brandtzaeg, a significant figure in the discipline of mucosal immunology, and Finn-Eirik Johansen from LIIPAT in Norway (12).