The present invention relates to a peptide capable of binding to an immunoglobulin, and to a fusion protein containing such a peptide. The present invention also relates to a pharmaceutical composition for the treatment or prevention of a disease caused by binding between Clq and an immunoglobulin, which comprises a peptide capable of binding to the immunoglobulin or a fusion protein with such a peptide, and to the like. The pharmaceutical composition provided by the present invention is effective particularly in treating arthritis and rheumatism.
