Arthritis-related B cell epitopes in collagen II are conformation-dependent and sterically privileged in accessible sites of cartilage collagen fibrils.
In collagen-induced arthritis, a murine autoimmune model for rheumatoid arthritis, immunization with native but not heat-denatured cartilage-specific collagen type II (CII) induces a B cell response that largely contributes to arthritogenicity. Previously, we have shown that monoclonal antibodies established from arthritis prone DBA/1 mice require the triple-helical conformation of their epitopes for antigen recognition. Here, we present a novel approach to characterize arthritis-related conformational epitopes by preparing a panel of 130 chimeric collagen X/CII molecules. The insertion of a series of CII cassettes into the triple-helical recombinant collagen X allowed for the first time the identification of five triple-helical immunodominant domains of 5-11 amino acid length, to which 75% of 36 monoclonal antibodies bound. A consensus motif, "R G hydrophobic," was found in all immunodominant epitopes. The antibodies were encoded by a certain combination of V-genes in germline configuration, indicating a role of the consensus motif in V-gene selection. The immunodominant domains are spread over the entire monomeric CII molecule with no apparent order; however, a highly organized arrangement became apparent when the CII molecules were displayed in the quarter-staggered assembly within a fibril. This discrete epitope organization most likely reflects structural constraints that restrict the exposure of CII epitopes on the surface of heterotypically assembled cartilage fibrils. Thus, our data suggest a preimmune B cell selection process that is biased by the accessibility of CII determinants in the intact cartilage tissue.
Schulte
S
S
Department of Internal Medicine III, University of Erlangen-Nürnberg, Germany.
Unger
C
C
Mo
J A
JA
Wendler
O
O
Bauer
E
E
Frischholz
S
S
von der Mark
K
K
Kalden
J R
JR
Holmdahl
R
R
Burkhardt
H
H
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D000918:Antibody Specificity; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D003094:Collagen / Q000235:genetics / Q000276:immunology*; D018604:Epitope Mapping; D018985:Epitopes, B-Lymphocyte / Q000032:analysis*; D007249:Inflammation / Q000139:chemically induced; D051379:Mice; D008811:Mice, Inbred DBA; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013583:Synovial Membrane / Q000187:drug effects
D000911:Antibodies, Monoclonal; D018985:Epitopes, B-Lymphocyte; D011993:Recombinant Fusion Proteins; D003094:Collagen