Isotype analysis of the anti-CENP-B anticentromere autoantibody: evidence for restricted clonality.

Utilizing the centromere B fusion protein (CENP-B) and specific, matched monoclonal antiisotype reagents in an enzyme-linked immunosorbent assay, we found that anti-CENP-B autoantibodies were skewed to the IgG1 isotype. The overall kappa:lambda light chain ratio was 2:1, although several individual sera showed a strong predominance of one of the light chains. Isoelectric focusing of light chain-skewed sera showed polyclonal patterns. Our findings are consistent with the anti-CENP-B autoantibody response being a chronic, antigen-driven response.

Human autoantibody to topoisomerase II.

The rheumatic diseases are characterized by the production of autoantibodies that are usually directed against components of the cell nucleus. In this communication, we describe autoantibodies that recognize DNA topoisomerase II (anti-topoII) present in the serum of a patient with systemic lupus erythematosus. Several lines of evidence indicate that this antibody recognizes topoisomerase II. First, it binds to the native enzyme in soluble extracts prepared from isolated chromosomes and effectively depletes such extracts of active enzyme. Second, the serum binds to topoisomerase II in immunoblots of mitotic chromosomes and chromosome scaffolds. Finally, the antiserum binds strongly to a fusion protein encoded by a cloned cDNA and expressed in Escherichia coli that (based on immunological evidence) represents the carboxy-terminal portion of chicken topoisomerase II. Autoantibodies such as the one described here may provide useful reagents for the study of human topoisomerase II.

Analysis of anticentromere autoantibodies using cloned autoantigen CENP-B.

A cDNA clone encoding CENP-B, the 80-kDa human centromere autoantigen, was used to construct a panel of hybrid proteins containing four different regions of CENP-B. These have allowed us to identify three independent epitopes on CENP-B that are targets of autoantibodies. Two of these are recognized concurrently in greater than or equal to 90% of patient sera containing anticentromere autoantibodies (ACA), conclusively demonstrating that this autoimmune response is polyclonal. When present and previous data are combined, ACA are shown to recognize at least five independent epitopes on CENP-B. A radioimmunoassay based on cloned CENP-B has demonstrated that sera from greater than or equal to 96% of patients with ACA recognize the cloned antigen, thus defining a region of the protein that is recognized by virtually all patients with ACA. These findings have significant implications for models that seek to explain the origin of ACA and for the future detection of this group of autoantibodies in the clinical setting.

Familial discoid lupus erythematosus associated with heterozygote C2 deficiency.

Two siblings with chronic discoid lupus erythematosus and several family members were found with heterozygous C2 deficiency. An association with histocompatibility markers HLA-B18 and HLA-Dw2 was demonstrated, and the slow allotype of factor B was present. Linkage studies in this family suggested a close linkage between the C2 deficiency gene and genes coding for B18, Dw2, and BfS antigens. One HLA-ACB/DBf recombinant was observed showing closer linkage between HLA-D and Bf than between HLA-B and Bf.