Characterization of C3dg binding to a recess formed between short consensus repeats 1 and 2 of complement receptor type 2 (CR2; CD21).
To allow for a better characterization of the ligand binding structures of human complement receptor type 2 (CR2; CD21), we have established an IgG1 kappa mouse mAb, FE8, that interferes efficiently with binding of C3dg and EBV to CR2. In contrast to mAb OKB7, the only well-characterized mAb with similar specificity, mAb FE8 blocked binding of soluble C3dg or particles carrying multiple copies of surface-bound C3dg to CR2 or induced complete removal of these ligands from the receptor. In vitro EBV infection of B lymphocytes, on the other hand, was abrogated by mAbs FE8 and OKB7 with similar dose-response characteristics. As FE8 was shown to recognize a discontinuous epitope, a series of overlapping peptides derived from SCR1 and -2 and immobilized on cellulose was screened with FE8. The results suggest that up to five discontinuous sequences contributed to the epitope. The sequence 63-EYFNKYS-69, located between the two SCR units, reacted most intensively. Two other sequences, 16-YYSTPI-21 and 105-NGNKSVWCQANN-116, are located between Cys1 and Cys2 of SCR1 and around Cys3 of SCR2, respectively. Based on the solution structure for two factor H SCRs, a three-dimensional model of SCR1 and -2 was generated. The FE8 binding peptide sequences were located in relative proximity to each other, bounding the recess formed between SCR1 and -2. This potential of mAb FE8 is currently unique and may be exploited for interfering with conditions of unwanted recognition of C3dg-coated structures by the immune system.
Prodinger
W M
WM
Institut für Hygiene, University of Innsbruck, Austria.
Schwendinger
M G
MG
Schoch
J
J
Köchle
M
M
Larcher
C
C
Dierich
M P
MP
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology / Q000494:pharmacology; D000937:Antigen-Antibody Reactions; D001665:Binding Sites; D001667:Binding, Competitive; D003179:Complement C3b / Q000378:metabolism*; D003198:Computer Simulation; D016384:Consensus Sequence; D000939:Epitopes / Q000276:immunology; D005260:Female; D004854:Herpesvirus 4, Human / Q000378:metabolism; D006801:Humans; D006825:Hybridomas / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008863:Microspheres; D018448:Models, Immunological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism*; D019151:Peptide Library; D011485:Protein Binding; D011487:Protein Conformation; D017464:Receptors, Complement 3d / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D020449:Repetitive Sequences, Amino Acid; D012995:Solubility
D000911:Antibodies, Monoclonal; D000939:Epitopes; D010446:Peptide Fragments; D019151:Peptide Library; D017464:Receptors, Complement 3d; C045477:complement C3d,g; D003179:Complement C3b