The present invention relates to a monoclonal antibody having excellent immunosuppressive activity or an antigen binding fragment thereof. More specifically, the present invention relates to a monoclonal antibody or an antigen binding fragment thereof, which binds to a peptide consisting an amino acid sequence represented by SSVLYGGPPSAA (SEQ ID NO: 1) or a conjugate of the peptide and a pharmaceutically acceptable carrier, the monoclonal antibody or an antigen binding fragment thereof having a higher binding affinity for core histone than for histone H1.
