A cross-reactive idiotype in scleroderma

Abstract

SUMMARYAutoantibodies to centromere proteins (anti-CENPs) and to topoisomerase-I are highly specific for scleroderma. Unlike most autoantibodies in other diseases, these autoantibodies are mutually exclusive. We have analysed the idiotypes (Ids) expressed by anti-CENP-B, antitopoisomerase-I, and IgGs from 20 scleroderma patients. Rabbit anti-Ids were prepared to antitopoisomerase-I from two scleroderma patients, and to anti-CENP-B from four patients. These six anti-Ids were used to study the purified autoantibodies from 20 scleroderma patients: four antitopoisomerase-I, 10 anti-CENP-B, and six purified IgG from scleroderma patients who were negative for both autoantibodies. In addition, we studied sera from 40 normal autoantibody-negative controls, and sera and purified immunoglobulins from 17 systemic lupus erythematosus (SLE) patients containing high titres of anti-double-stranded DNA, and/or autoantibodies to extractable nuclear antigens (ENA). Using direct binding, and competitive inhibition ELISAs and immunoblots, we identified an Id present in the heavy chains of all the affinity-purified antitopoisomerase-I, and anti-CENP-B. Interestingly, this Id was also present in the immunoglobulins of the scleroderma patients who had neither of the two autoantibodies. By contrast, cross-reactive Id-EM was not found in the sera or immunoglobulins from 17 SLE patients, or in the sera from 40 normal subjects. Several samples from two patients showed that this cross-reactive Id-EM was stable over time. The scleroderma disease-specific autoantibodies may be identified through a common structural feature at the variable region of the heavy chain: cross-reactive Id-EM.

Anticentromere Autoantibodies in Patients without Raynaud's Disease or Systemic Sclerosis

“…Taken altogether, our data suggest that the origin of these ACA may be different than that in Raynaud's disease and SSc. Our data further supports the high specificity and homogeneity of the humoral response that is unique of SSc and Raynaud's disease (12).…”

“…UNUSUAL ANTICENTROMERE ANTIBODIES serum immunoglobulins from normal individuals or patients with systemic lupus erythematosus (12,16). Furthermore, after exhaustive absorption of serum ATA and ACA, we showed that CRI-EM, while present in the affinity purified autoantibodies, was absent from the other immunoglobulins in the same individual (12,13).…”

“…Our studies suggest that these antibodies derive from the same precursor B cell. They share a heavy chain (VH) idiotype called CRI-EM (12,13,16). CRI-EM is present also in the VH of immunoglobulins from SSc patients who are negative for ACA and ATA (12).…”

“…Anti-CENP-B antibodies were affinity purified on recombinant CENP-B (1) coupled to Sepharose 4B gel (Pharmacia, Uppsala, Sweden) as described (12,13).…”

“…Three strips were incubated with each serum. After thorough washes each of the three strips per serum was incubated with one of the specific heavy chain peroxidase-labeled rabbit anti-human IgG, IgM, or IgA antibodies, respectively (Dakopatts) (12,13). The strips were developed as described above.…”