PROBLEM TO BE SOLVED: To provide an immunosuppressant as an agent, e.g. for preventing and/or treating an autoimmune disease, rejection after organ transplant, an allergic disease or an inflammatory disease, and to provide an immunostimulator as an agent for preventing and/or treating deceases selected from a cancer, an immunodeficiency disease and an infectious disease.SOLUTION: This immunosuppressant includes (1) an isolated monoclonal antibody to protein having an amino acid sequence in sequence numbers 1 to 6, or (2) an antibody recognizing (i) protein having an amino acid sequence in sequence numbers 1 to 6 and (ii) any receptor selected from a B-cell receptor or a B-cell receptor composite, an activated Fc receptor, a CD14/TLR4 composite and Fc&egr；RI, together. This immunostimulator includes (1) an isolated monoclonal antibody to protein having an amino acid sequence in sequence numbers 1 to 6, or (2) isolated polypeptide made of an optional region in the extracellular region of protein having an amino acid sequence in sequence numbers 1 to 6.【課題】自己免疫疾患、臓器移植後の拒絶反応、アレルギー性疾患または炎症性疾患に対する予防および／または治療剤等の免疫抑制剤及び癌、免疫不全症および感染症から選択される疾患の予防および／または治療剤である免疫賦活剤の提供。【解決手段】（１）配列番号１～６のアミノ酸配列を有するタンパク質に対する単離モノクローナル抗体、または（２）（ｉ）配列番号１～６のアミノ酸配列を有するタンパク質および（ii）Ｂ細胞受容体もしくはＢ細胞受容体複合体、活性化Ｆｃ受容体、ＣＤ１４／ＴＬＲ４複合体およびＦｃεＲＩから選択されるいずれかの受容体をともに認識する抗体を含む免疫抑制剤、（１）配列番号１～６のアミノ酸配列を有するタンパク質に対する単離モノクローナル抗体、または（２）配列番号１～６のアミノ酸配列を有するタンパク質の細胞外領域内の任意の領域からなる単離ポリペプチドを含む免疫賦活剤。【選択図】なし
