This disclosure provides,inter alia, proteins that bind to FcRn,e.g., immunoglobulins that inhibit FcRn with high affinity and selectivity. The FcRn-binding proteins can be used to treat a variety of disorders including autoimmune disorders.本發明揭示案尤其提供結合FcRn之蛋白質,例如以高親和力及選擇性抑制FcRn之免疫球蛋白。該等FcRn結合蛋白可用於治療包括自體免疫病症之多種病症。