The present invention features antibodies that have high binding affinity to human neonatal Fc receptor (FcRn). These anti-FcRn antibodies are useful, e.g., to promote clearance of autoantibodies in a subject, to suppress antigen presentation in a subject, to block an immune response, e.g., block an immune complex-based activation of the immune response in a subject, and to treat immunological diseases (e.g., autoimmune diseases) in a subject.