CD97 binds CD55

CD55 (or Decay Accelerating Factor; DAF) is a member of the regulators of complement activation (RCA) family. It protects host cells from complement system attack by binding to C3b and C4b preventing formation of the membrane attack complex. CD97 is a member of the Adhesion class or LNB subfamily of family B GPCRs, characterized by long N-terminal regions containing domains contain multiple tandem epidermal growth factor (EGF)-like repeats in their N-termini (Foord et al. 2002). CD97 is constitutively expressed on granulocytes and monocytes and is rapidly up-regulated on activated T and B cells. It is known to have many splice forms containing different numbers of EGF domains, consequently binding CD55 with differing affinities. The highest affinity variant has three EGF domains. The leukocyte-restricted expression pattern of CD97, and the presence of both CD97 and CD55 in arthritic joints suggest a possible role in adhesion and signaling within the inflammatory and immune responses (Lin et al. 2001).

CD55，亦称衰变加速因子（Decay Accelerating Factor；DAF），是补体激活调节因子（Regulators of Complement Activation；RCA）家族的成员。该因子通过结合C3b和C4b，防止形成膜攻击复合物，从而保护宿主细胞免受补体系统的攻击。CD97是B族G蛋白偶联受体（GPCRs）的粘附类或LNB亚家族的成员，其特征在于N端区域含有多个串联的表皮生长因子（EGF）样重复序列（Foord等，2002年）。CD97在粒细胞和单核细胞上恒定表达，并在活化的T和B细胞上迅速上调。已知CD97存在多种剪接形式，含有不同数量的EGF结构域，因此与CD55的结合亲和力各异。亲和力最高的变体含有三个EGF结构域。CD97在白细胞中的特异性表达模式以及其在关节炎关节中的存在，提示其在炎症和免疫反应中的粘附和信号传导可能发挥重要作用（Lin等，2001年）。