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).
Hamann, J, van Schijndel, GM, Vogel, B, van Lier, RA
Knott, V, Evans, D, Chaudhry, Y, Gordon, S, Stacey, M, Lea, S, Saxby, C, Handford, PA, Lin, HH, McKnight, AJ
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