The present invention provides an antibody comprising an antigen binding domain which binds to human IL-12 and human IL-23. The antibody binds human IL-12p40 existing as a monomer (human IL-12p40) and as a homodimer (human IL-12p80) and the antibody inhibits the binding of human IL-12 to human IL-12Rβ2 and human IL-23 to human IL-23R but does not inhibit the binding of human IL-12 or human IL-23 or human IL-12p40 or human IL-12p80 to human IL-12Rβ1.本發明提供一種抗體,其包含與人類IL-12及人類IL-23結合之抗原結合域。該抗體與以單體形式(人類IL-12p40)及以同元二聚體形式(人類IL-12p80)存在之人類IL-12p40結合且該抗體抑制人類IL-12與人類IL-12Rβ2之結合及人類IL-23與人類IL-23R之結合,但不抑制人類IL-12或人類IL-23或人類IL-12p40或人類IL-12p80與人類IL-12Rβ1之結合。