Compositions and methods are provided for treating diseases associated with CD100, including certain autoimmune diseases, inflammatory diseases, and cancers. In particular, anti-CD100 monoclonal antibodies have been developed to neutralize CD100.Se proporcionan composiciones y métodos para tratar enfermedades asociadas con CD100, incluyendo ciertas enfermedades autoinmunitarias, enfermedades inflamatorias, y cánceres. En particular, se han desarrollado los anticuerpos anti-CD100 para neutralizar CD100.