PIGR and bacterial meningitis: Notably, the type 2 IgA1 protease of Neisseria meningitidis, a causative agent of bacterial meningitis, interacts with the Cα3 residues of the Cα2–Cα3 interface also bound by FcαRI, pIgR and Fcα/μR, whereas the type 2 IgA1 protease of Haemophilus influenzae contacts a different set of Cα3 residues that are implicated in binding to pIgR [19].