Molecular basis for the cross-reactive idiotypes on human anti-IgG autoantibodies (rheumatoid factors)

High titres of anti-IgG autoantibodies (rheumatoid factors, RF) are characteristic of patients with rheumatoid arthritis, Sjögren's syndrome, and mixed cryoglobulinaemia, and may contribute to immune complex formation and tissue damage. The monoclonal RFs from cryoglobulinaemia patients frequently display cross-reactive idiotypes. The genetic basis for the cross-reactive idiotypes on RF autoantibodies has not been determined. To clarify structural and genetic relationships among RFs from unrelated subjects, a series of anti-peptide antibodies have been generated that define primary sequence-dependent idiotypes on RF heavy and light chains. Multiple monoclonal and polyclonal RFs from unrelated individuals have been probed by Western blotting with the anti-idiotypic reagents. The results show that sequences in the kappa light chain variable region represent a common structural element among RF autoantibodies. This hypothesis is confirmed by the cloning and sequencing of the conserved germline variable region gene which encodes human RF kappa chains.

D-penicillamine-induced crescentic glomerulonephritis and antimyeloperoxidase antibodies in a patient with scleroderma. Case report and review of the literature

Therapeutic use of D-penicillamine has been associated with a range of adverse effects. We present a patient with scleroderma, treated with D-penicillamine for 5 years, who developed severe renal failure due to rapidly progressive glomerulonephritis with both crescents and subepithelial immune deposits on renal biopsy. Serological findings included perinuclear antineutrophil cytoplasmic antibodies and antihistone antibodies. She was treated with cyclophosphamide, prednisone, discontinuation of D-penicillamine, and hemodialysis. Therapy resulted in partial recovery of renal function. The clinical course of our patient is in keeping with D-penicillamine-induced chronic membranous nephropathy, followed by rapidly progressive crescentic glomerulonephritis. We discuss the effects of D-penicillamine in our patient, and review the literature on immune-mediated renal disease associated with the use of this drug.

Stiffness of the rib cage in a subset of rheumatoid patients

In a previous investigation of lung function in patients with rheumatoid arthritis (RA), we observed that some patients had significant dysfunction of their chest wall mechanics without pleural disease that could contribute to their respiratory symptoms. To investigate further the chest wall functions of patients with RA, we selected 10 female lifetime nonsmoking patients with RA and compared them to 10 paid normal volunteers in detailed functional evaluations of lung and chest wall. Patients with significant airflow limitation were excluded from this study. We found a significant 7% reduction in total lung capacity in the RA patients without significant change in lung compliance. However, we found a significant reduction in rib cage compliance in patients with RA (0.044 +/- 0.006 L/cmH2O vs. 0.064 +/- 0.012 in controls), which was associated with a significant 38% reduction in expansion of the rib cage volume during various breathing maneuvers. These changes occurred in the absence of lung or pleural disease. This study documents that patients with RA have limited expansion of rib cage relative to abdomen, thus rib cage restriction and stiffness, which may contribute to reduced lung volume. The shift of thoracoabdominal breathing configuration observed in patients with RA will likely reduce the effectiveness of breathing muscles and thus could contribute to the dyspnea sensation experienced by patients with RA.

Isolation and characterization of human VkIII germ-line genes. Implications for the molecular basis of human VkIII light chain diversity

To understand the relative importance of germ-line genes in the generation of the functional human antibody repertoire, it is first necessary to define the number of variable region genes and to determine their fine structure. We have focused on the human VkIII variable region gene family because of its association with autoantibodies. A human genomic library was screened with a VkIII cDNA probe and subsequently with a VkIII germ-line gene probe. Seven different VkIII clones were isolated and characterized by restriction mapping and sequence analyses. Three clones have identical restriction enzyme sites over a 12-kilobase (kb) region, contain identical sequences over an 895-base pair (bp) region, and thus are likely to be different isolates of the same human VkIII gene. Another two clones have identical restriction enzyme sites over a 5-kb region, are identical over a stretch of 905 bp sequenced, and likely represent independent isolates of another human VkIII gene. The remaining two VkIII clones consist of two additional VkIII genes which are homologous to each other, but are quite different from the first two VkIII genes. Thus, four new human VkIII genes were defined. Together with four other VkIII genes previously isolated by other investigators, a total of eight human VkIII germ-like genes have now been described. A comparison of the deduced amino acid sequences of these genes with the reported amino acid sequences of all human VkIII light chains suggests that at least one additional VkIII gene exists in the germ line. Among the eight identified human germ-line VkIII genes, three are pseudogenes. Of the remaining five potential functional genes, one gene seems to encode a majority of the VkIII light chains which have been sequenced. Possible explanations for this phenomenon are discussed.

Isolation and characterization of human VkIII germ-line genes. Implications for the molecular basis of human VkIII light chain diversity

To understand the relative importance of germ-line genes in the generation of the functional human antibody repertoire, it is first necessary to define the number of variable region genes and to determine their fine structure. We have focused on the human VkIII variable region gene family because of its association with autoantibodies. A human genomic library was screened with a VkIII cDNA probe and subsequently with a VkIII germ-line gene probe. Seven different VkIII clones were isolated and characterized by restriction mapping and sequence analyses. Three clones have identical restriction enzyme sites over a 12-kilobase (kb) region, contain identical sequences over an 895-base pair (bp) region, and thus are likely to be different isolates of the same human VkIII gene. Another two clones have identical restriction enzyme sites over a 5-kb region, are identical over a stretch of 905 bp sequenced, and likely represent independent isolates of another human VkIII gene. The remaining two VkIII clones consist of two additional VkIII genes which are homologous to each other, but are quite different from the first two VkIII genes. Thus, four new human VkIII genes were defined. Together with four other VkIII genes previously isolated by other investigators, a total of eight human VkIII germ-like genes have now been described. A comparison of the deduced amino acid sequences of these genes with the reported amino acid sequences of all human VkIII light chains suggests that at least one additional VkIII gene exists in the germ line. Among the eight identified human germ-line VkIII genes, three are pseudogenes. Of the remaining five potential functional genes, one gene seems to encode a majority of the VkIII light chains which have been sequenced. Possible explanations for this phenomenon are discussed.

Rheumatoid factor and immune networks

Rheumatoid factors represent a normal component of the immune network. The autoantibodies promote complement fixation and clearance of immune complexes. They amplify the avidity of polyclonally induced IgG. Genes related to the primary structure of rheumatoid-factor light chains are widely distributed in the human population and have been conserved during the evolution and dispersion of the species. Products of these genes may be detected with anti-idiotypic antibodies against synthetic peptides corresponding to individual hypervariable regions on rheumatoid-factor light chains. Such anti-peptide antibodies provide unique reagents for analyzing the genetics of immunoglobulins in outbred populations. Precursors of rheumatoid factor are abundant among immature B lymphocytes. Some of these cells may tend to localize to mucosal surfaces, where they are stimulated directly by pathogenic microorganisms with polyclonal B cell-activating properties. Synthesis of rheumatoid factor regularly accompanies all secondary immune responses but is usually transient. Production of the autoantibody is T-cell dependent. The T cells may recognize antigen in an IgG-antigen immune complex that is processed and presented by B-cell precursors of rheumatoid factor. Rheumatoid factor-associated light-chain idiotypes are rare in serum IgG and on IgG myeloma proteins. They are common among monoclonal IgM proteins and on the surface of the malignant B cells from patients with chronic lymphatic leukemia. The rheumatoid factors that are produced by patients with mixed cryoglobulinemia, or primary Sjogren's syndrome can share idiotypic antigens with monoclonal rheumatoid factors. Rheumatoid factor synthesis in the diseases may reflect an abnormal proliferation of B-cells that is not antigen-driven and that can degenerate into malignancy. The rheumatoid factors in patients with rheumatoid arthritis are diverse and almost certainly represent the outcome of antigen-induced, T cell-dependent mechanisms. The antigens that drive the T cells have not been identified but could represent exogenous microorganisms, self components, or idiotypic antigens that fortuitously interact with rheumatoid factors.

Airways disease in rheumatoid arthritis patients. One element of a general exocrine dysfunction

Airflow limitation is a frequent finding in patients with rheumatic diseases. We have previously suggested that it is associated with autoimmune exocrinopathy in Sjögren's syndrome. To compare clinical features of patients with and without airways dysfunction and to further test the hypothesis of a link between airways disease and exocrinopathy, we prospectively studied 2 groups of 15 lifetime nonsmoker female patients with seropositive rheumatoid arthritis (RA). The 2 groups were similar in their clinical and immunologic features, but differed in terms of airways function. Salivary, lacrimal, and sweat gland dysfunction were significantly more prevalent or severe in the group with airways disease. Antinuclear antibodies were also more prominent in the patients with airways disease, but antibodies against RNP, SS-A, SS-B, and double-stranded DNA were not present in these patients. HLA-DR4 was found in 80% of the RA patients with airways disease and in 57% of those without airways disease. HLA-B8 and DR3 were equivalently distributed in both groups. This prospective study further documents the existence of small airways disease in RA and supports the view that autoimmune exocrinopathy predisposes to its expression.

Genetic analysis of human B cell hybridomas expressing a cross-reactive idiotype

We have examined the genetic basis for the expression of a human cross-reactive idiotype (CRI) commonly found on monoclonal IgM rheumatoid factors. The CRI was identified with a monoclonal antibody (17.109) and has been localized previously to the kappa-variable region. By using the human lymphoblastoid cell line WI-L2-729-HF2, and mononuclear cells from several sources, a panel of hybridomas was generated that produced 17.109 CRI-positive Ig. A recently cloned human germ-line V kappa III gene, Humkv305, served as a probe to identify genes which were rearranged and expressed in 17.109 CRI-positive and -negative hybridomas. This probe, when hybridized to human genomic DNA under stringent conditions, identified only two to five germ-line bands. In 10 separate 17.109 CRI-positive hybridoma clones, an additional rearranged V kappa band was identified. The probe did not anneal to rearranged V kappa bands in hybridoma clones that produced kappa-chains lacking the CRI. RNA dot-blot studies provided evidence for expression of genes hybridizing to the Humkv305 probe. The results indicate that the 17.109 CRI is a serologic marker for a single V kappa gene, or a small family of closely related V kappa genes, which is identified by the Humkv305 probe.

Genetic analysis of human B cell hybridomas expressing a cross-reactive idiotype

We have examined the genetic basis for the expression of a human cross-reactive idiotype (CRI) commonly found on monoclonal IgM rheumatoid factors. The CRI was identified with a monoclonal antibody (17.109) and has been localized previously to the kappa-variable region. By using the human lymphoblastoid cell line WI-L2-729-HF2, and mononuclear cells from several sources, a panel of hybridomas was generated that produced 17.109 CRI-positive Ig. A recently cloned human germ-line V kappa III gene, Humkv305, served as a probe to identify genes which were rearranged and expressed in 17.109 CRI-positive and -negative hybridomas. This probe, when hybridized to human genomic DNA under stringent conditions, identified only two to five germ-line bands. In 10 separate 17.109 CRI-positive hybridoma clones, an additional rearranged V kappa band was identified. The probe did not anneal to rearranged V kappa bands in hybridoma clones that produced kappa-chains lacking the CRI. RNA dot-blot studies provided evidence for expression of genes hybridizing to the Humkv305 probe. The results indicate that the 17.109 CRI is a serologic marker for a single V kappa gene, or a small family of closely related V kappa genes, which is identified by the Humkv305 probe.

A conserved human germline V kappa gene directly encodes rheumatoid factor light chains

The full-length gene that encodes the light chain variable regions of an idiotypically related group of human IgM kappa rheumatoid factors (RFs) has been cloned and sequenced. The deduced amino acid sequence is identical to four separate RF proteins. These results prove that genes capable of encoding human anti-IgG autoantibody light chains without any somatic mutation are present in the kappa gene repertoire of normal people.

Genetic basis for the cross-reactive idiotypes on the light chains of human IgM anti-IgG autoantibodies

The role of immunoglobulin structural genes in the generation of autoantibodies in humans has not been elucidated. Human monoclonal IgM anti-IgG autoantibodies (rheumatoid factors, RFs) from unrelated people often share idiotypic antigens. Antibodies against synthetic peptides have localized two of the shared idiotypic determinants to the second and third complementarity-determining regions of the kappa light chain. The reported sequences of several human RF light chains are remarkably homologous in these regions. Animal studies have shown that some shared idiotypic antigens represent serological markers for immunoglobulin variable (V)-region genes. Therefore, we hypothesized that human RF light chains derived from a single germ-line gene, designated V kappa-(RF), or from a small family of very closely related genes. In the present experiments, we have isolated and sequenced two human V kappa germ-line genes that encode kappa light chains, which are identical or closely related to the light chains of human RF. The data indicate that the shared idiotypic antigens on RF are phenotypic markers for a kappa V-region gene that is highly conserved in the human population. The results also imply that the light chains of IgM anti-IgG autoantibodies can be encoded by germ-line genes without any somatic mutation.