John A. Mo

Collagen induced arthritis as an experimental model for rheumatoid arthritis

The type II collagen (CII) induced arthritis animal model (CIA) provides opportunities to study the nature of autoimmune reactions leading to arthritis and may be used as a model for rheumatoid arthritis (RA). Thus, in similarity with RA, the CIA model, when induced with autologous CII, shows a chronic and progressive disease course. The susceptibility to both RA and CIA are correlated to the expression of certain MHC class II allotype genes. In both diseases are autoantibodies to CII and rheumatoid factors produced. Immunohistopathology of affected joints show in both diseases a dominance of activated macrophages/fibroblasts with a significant infiltration of activated T cells and an infiltration of granulocytes. We do here suggest that both RA and CIA are dependent on a synergy between delayed type hypersensitivity and immune complex mediated inflammarory mechanisems and that CIA provides opportunities for studies of immunspecific reactions leading to arthritis.

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.

Binding of autoreactive mouse anti-type II collagen antibodies derived from the primary and the secondary immune response investigated with the biosensor technique.

The reactivity of autoantibodies to type II collagen, secreted by B cells isolated from the primary and the secondary immune response to rat type II collagen in DBA/1 mice, was investigated using BIAcore 2000 instrumentation. Assays were performed on both collagen and antibody surfaces. These assays demonstrated a 100-fold difference in affinity between primary and secondary immune response antibodies. The difference in affinity was almost entirely due to differences in the dissociation rate constant. Somatic mutations in secondary clones were in one case associated with a 3-4-fold difference in affinity and in another case appeared to be without any effect on the binding activity.

Germline-encoded IgG antibodies bind mouse cartilage in vivo: epitope- and idiotype-specific binding and inhibition.

Autoantibodies specifie for type‐II collagen (CII) occur in mice and rats with collagen‐induced arthritis (CIA). The binding in vitro and in vivo of mouse monoclonal antibodies (MoAbs) specific for separate epitopes in CII have been investigated. Two‐day‐old mice were injected intraperitoneally (i. p.) with the anti‐CII antibody CIID3 in both unlabelled and biotinylated form. It was found that antibodies binding to the same epilope in CII in vivo can inhibit others from binding in an epitope‐specific fashion. The binding in vivo and in vitro of anti‐CII antibodies could be inhibited also by an anti‐idiotypic rat antiserum produced against the D3 antibody. The anti‐idiotypic antiserum inhibited the binding of the antibody D3 and the idiotypically related antibody C2. The cDNAs of anti‐CII antibodies D3, C2, and F4 were sequeneed and found to contain germline encoded V‐genes. apparently without somatic mutations. The variable heavy chain of D3 and C2 both expressed the same VH rearrangement, confirming that they share idiotypes. This report demonstrates that CII‐specific germline‐encoded IgG autoantibodies bind specifically to normal cartilage in vivo via their combining site.

Chronicity of tissue-specific experimental autoimmune disease: a role for B cells?

We will use here the freedom given to authors of a review article, not only to summarize data, but also to generalize and speculate about the nature of the subject: chronicity of the development of tissue-specific autoimmune disease. Autoimmune diseases are often referred to as being caused by one principal mechanism, the failure to distinguish self from non-self. The weakness of this principal view is two-sided. First, the immune systems definition of self is relative. Second, various autoimmune diseases are very diverse in their pathogenesis, thereby obscuring the definition. The principles of how the immune system distinguishes self from non-self have been clarified to a significant extent during recent years, mainly by well-defined animal models. It is apparent that the view of what is self to the immune system is related to the environment and the context in which the structure is presented. Before discussing how chronicity in autoimmune disease evolves, we need to summarize the principles of how autoreactive T and B cells are controlled. These principles include: 1) Deletion. Lymphocytes carrying receptors of enough affinity for abundant self antigens, in particular if these are cell-bound, are eliminated most likely, by an active suicide mechanism (apoptosis). 2) Functional deficit/deviation. Recognition of structures in an environment which will not provide support to trigger full activation of the responding cell often leads to functional deficit (anergy) or deviation of the cytokine response.

Pathogenic Autoreactive B Cells Are Not Negatively Selected toward Matrix Protein Collagen II

We have addressed the importance of B cell tolerance to collagen type II, a matrix protein, which is a target in rheumatoid arthritis (RA) and its mouse models. We generated a germline-encoded anti-collagen type II (CII) IgH replacement anti-C1 B cell mouse strain (ACB) to investigate how B cell tolerance to CII, a matrix protein, is subverted and to further understand pathogenesis of RA. Phenotypic analysis revealed that CII-specific B cells were surprisingly neither deleted nor anergized. Instead, they were readily detected in all lymphoid organs. Spontaneously produced autoantibodies could bind directly to cartilage surface without detectable pathology. However, exaggerated arthritis was seen after injection of anti-CII Abs specific for other epitopes. In addition, Abs from CII-specific hybridomas generated from ACB mice induced arthritis. Interestingly, IgH/L chain sequence data in B cell hybridomas revealed a lack of somatic mutations in autoreactive B cells. The ACB model provides the first possibility, to our knowledge, to study B cell tolerance to a matrix protein, and the observations made in the study could not be predicted from previous models. B cell-reactive epitopes on CII are largely shared between human RA and rodent CII-induced arthritis; this study, therefore, has important implications for further understanding of pathological processes in autoimmune diseases like RA.

Correction: Pathogenic Autoreactive B Cells Are Not Negatively Selected toward Matrix Protein Collagen II

Cao, D., I. Khmaladze, H. Jia, E. Bajtner, K. S. Nandakumar, T. Blom, J. A. Mo, and R. Holmdahl. 2011. Pathogenic autoreactive B cells are not negatively selected toward matrix protein collagen II. J Immunol . 187: [4451–4458][1]. There were several errors in the legend for [Fig. 3][2]. In the