Differential use of immunoglobulin light chain genes and B lymphocyte expansion at sites of disease in rheumatoid arthritis (RA) compared with circulating B lymphocytes

Judging disease activity in rheumatoid arthritis by serum free kappa and lambda light chain levels

The study aimed to evaluate the levels of serum free kappa (κ) and lambda (λ) light chains in patients with rheumatoid arthritis (RA) as well as exploring the association between serum free κ and λ light chains and activity of RA. For this purpose, healthy individuals and patients with active RA and RA in remission were enrolled, and their serum levels of free κ and λ light chains were measured using rate nephelometry. The diagnostic accuracy of serum free κ and λ light chains was evaluated by receiver operating characteristic curves and 95% confidence intervals for areas under the curve (AUC). The results obtained indicated that the levels of serum free κ and λ light chains in patients with active RA were significantly higher than those of patients in remission and of healthy controls (p < 0.05). Further, the AUC values in patients with active RA were 0.871 for free κ light chain and 0.781 for free λ light chain. When the optimal cut-off point for serum κ light chain was 8.02 g/L, the maximum sensitivity and specificity were 82.5% and 82.5%, respectively, and when the optimal cut-off point for serum λ light chain was 3.57 g/L, the maximum sensitivity and specificity were 80% and 82.5%, respectively. It was thus found that serum levels of free κ and λ light chains were positively correlated with disease activity in RA, the Disease Activity Score 28 (DAS28), and values for C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), platelet count (PLT), rheumatoid factor (RF), and anticitrullinated protein antibody (ACPA) (p < 0.05). In conclusion, high serum levels of free κ and λ light chains in patients with active RA are closely correlated with disease activity parameters including DAS28, CRP, ESR, PLT, RF, and ACPA. Thus, the above-mentioned levels of serum free κ and λ light chains may be used as important indicators of activity of RA.

B cells in autoimmune diseases: insights from analyses of immunoglobulin variable (Ig V) gene usage

The role of B cells in autoimmune diseases has not been fully elucidated. It is also unclear whether breaking of B cell tolerance in patients with autoimmune diseases is due to underlying defects in the molecular mechanisms involved in the arrangement of antibody genes or deficiencies in the subsequent selective influences that shape the antibody repertoire. Analysis of immunoglobulin (Ig) variable (V) gene usage is beginning to provide answers to some of these questions. Such analyses have identified some differences in the basic Ig V gene repertoire of patients with autoimmune diseases compared to healthy controls, even though none of these differences can be considered major. Defects in positive and negative selection, mutational targeting and, in some cases, receptor editing have also been detected. In addition, analysis of Ig V gene usage in target organs and tissues of patients with autoimmune diseases has clearly demonstrated that there is a highly compartmentalized clonal expansion of B cells driven by a limited number of antigens in these tissues. Great progress has been made in the structural and functional characterization of disease-associated antibodies, largely because of the development of the combinatorial library technique. Use of antibodies generated by this technique offers great promise in identifying B cell epitopes on known target antigens and in gaining greater insights into the pathogenic role of B cells in both B and T cell mediated autoimmune diseases.

Immunoglobulin light chain repertoire in chronic lymphocytic leukemia

Immunoglobulin kappa (IGK) and immunoglobulin lambda (IGL) light chain repertoire was analyzed in 276 chronic lymphocytic leukemia (CLL) cases and compared with the relevant repertoires from normal, autoreactive, and neoplastic cells. Twenty-one functional IGKV genes were used in IGKV-J rearrangements of 179 kappa-CLL cases; the most frequent genes were IGKV3-20(A27), IGKV1-39/1D-39(O2/O12), IGKV1-5(L12), IGKV4-1(B3), and IGKV2-30(A17); 90 (50.3%) of 179 IGK sequences were mutated (similarity < 98%). Twenty functional IGLV genes were used in IGLV-J rearrangements of 97 lambda-CLL cases; the most frequent genes were IGLV3-21(VL2-14), IGLV2-8(VL1-2), and IGLV2-14(VL1-4); 44 of 97 IGL sequences (45.4%) were mutated. Subsets with "CLL-biased" homologous complementarity-determining region 3 (CDR3) were identified: (1) IGKV2-30-IGKJ2, 7 sequences with homologous kappa CDR3 (KCDR3), 5 of 7 associated with homologous IGHV4-34 heavy chains; (2) IGKV1-39/1D-39-IGKJ1/4, 4 unmutated sequences with homologous KCDR3, 2 of 4 associated with homologous IGHV4-39 heavy chains; (3) IGKV1-5-IGKJ1/3, 4 sequences with homologous KCDR3, 2 of 4 associated with unmutated nonhomologous IGHV4-39 heavy chains; (4) IGLV1-44-IGLJ2/3, 2 sequences with homologous lambda CDR3 (LCDR3), associated with homologous IGHV4-b heavy chains; and (5) IGLV3-21-IGLJ2/3, 9 sequences with homologous LCDR3, 3 of 9 associated with homologous IGHV3-21 heavy chains. The existence of subsets that comprise given IGKV-J/IGLV-J domains associated with IGHV-D-J domains that display homologous CDR3 provides further evidence for the role of antigen in CLL pathogenesis.

Oligoclonal B lymphocyte expansion in the synovium of a patient with Behçet's disease

OBJECTIVE

Plasma cell infiltration is observed in recurrent arthritis associated with Behçet's disease (BD). The immune mechanism underlying B lymphocyte proliferation in the synovium is unclear. One hypothesis involves nonspecific polyclonal activation and another involves antigen-driven activation. The present study was undertaken to test both hypotheses and identify immunoglobulin genes that are clonally expanded in the synovium.

METHODS

Peripheral blood lymphocytes (PBL) and synovial cells from a patient with BD and PBL from a healthy control subject were obtained. Complementarity-determining region 3 (CDR3) fingerprinting analysis and nucleotide sequence analysis of Ig transcripts derived from clonally expanded B lymphocytes were performed in parallel.

RESULTS

Of 44 mu heavy chain clones of the VH4 family identified in the synovial tissue from the BD patient, 8 clones showed identical nucleotide sequences, and therefore, 18.2% were clonally expanded. For y heavy chain, 4 of 50 clones of the VH3 family showed nearly identical sequences; therefore, 4-8% were clonally expanded. The kappa light chain did not show a dominant band, but a clone with a 12-amino acid CDR3 showed 3% clonal expansion. Somatic mutations were frequently observed, with a high ratio of replacement to silent mutations in the CDRs compared with the framework regions. Three Ig genes expressed in the clonally expanded B lymphocytes were derived from germline gene segments reported to be involved in the production of autoantibodies.

CONCLUSION

These results support the hypothesis that antigen-driven clonal B lymphocyte proliferation occurs in the synovium in BD. Immunoglobulin transcripts clonally expanded in the synovium were identified.

Analysis of Ig kappa light chain gene variable regions expressed in the rheumatoid synovial B cells

Sequence analysis of antibody variable (V) regions can provide an insight regarding whether B cells have gone through an antigen-driven process of affinity maturation. In this study, we analyzed 16 V-regions of immunoglobulin (Ig) kappa light chain genes obtained from a cDNA library of a rheumatoid arthritis (RA) synovial tissue. A salient feature of our results is the high frequency utilization of germline V kappa I family genes, especially the O2/O12 gene (38%). All kappa V-regions showed extensive somatic hypermutation with 5.4% of an average mutation rate. Replacement to silent mutation (R/S) ratio in the complementarity determining region (CDR) was > 2.9 in 12 out of 16 clones, indicating that the majority of the RA synovial B cells had undergone affinity maturation. However, the four other clones showed R/S ratios of < 2.9 in the CDR despite a high mutation rate. In contrast to the previous reports, long CDR3 was not a characteristic feature of these clones. In summary, these data show the high frequency utilization of the germline O2/O12 gene and a high rate of mutation with an evidence of antigen selection in most of the Ig kappa genes expressed in the RA synovium.

Production and characterization of monoclonal IgM autoantibodies specific for the T-cell receptor

Natural autoantibodies to the T-cell receptor (Tcr) have been identified in all human sera. However, titer, epitope specificity, and isotype vary with physiological conditions, autoimmune diseases, and retroviral infections. The levels of anti-Tcr autoantibodies in rheumatoid arthritis (RA) patients are significantly higher than in normal individuals, and the autoantibodies are typically IgM. To obtain detailed information on these autoantibodies, we generated B-cell heterohybridomas secreting monoclonal IgM autoantibodies (mAAbs) from the synovial tissue and peripheral blood of RA patients. We selected clones secreting mAAbs that bound a major Vbeta epitope defined by a synthetic peptide that contains the CDR1 region of the Vbeta 8.1 gene product. From these we isolated a subset of seven mAAbs that bound a recombinant single-chain Valpha/Vbeta construct containing the peptide epitope and, also to JURKAT cells which express Vbeta 8.1. The mAAbs produced by these clones were distinct from each other in their V-region sequences. However, all the V regions were essentially identical to germline sequences in both the heavy and light chains. Heavy-chain CDR3 segments ranged in length from 17 to 26 residues, did not correspond to any known autoantibodies, and showed extensive N-region diversity in the V(D)J junctions. Five monoclonal autoantibodies use VH 3 genes, while the remaining two utilized VH 4 sequences. Light-chain variable regions used were Vkappa3 (two), Vlambda3 (four), and one Vlambda2. These autoantibodies derived their unique features from their CDR3 segments that could not be aligned with any known sequences.

The B lymphocyte in rheumatoid arthritis: recirculation of B lymphocytes between different joints and blood

In order to search for further evidence for a pathogenetic role of recirculating, antigen-driven B cell clones in rheumatoid arthritis (RA) rearranged VH genes were analysed for clonal relationship and somatic mutations from synovial tissue and peripheral blood of a patient with RA undergoing synovectomy of several finger joints. DNA was prepared from the synovial tissue of two finger joints and blood. PCR for the different VH families was performed with one specific oligonucleotide for each VH family and a mixture of JH-specific oligonucleotides. The PCR products were separated on a high resolution acrylamide gel differentiating one base pair difference of length. Transfer of the products onto a nylon membrane and hybridization with an oligonucleotide specific for the FR3 region revealed a polyclonal representation of rearranged VH1, VH3, VH4 and VH5 genes. The VH6 family, which is encoded by a single germline gene, was represented by few distinct bands, with some bands of identical height for both joints and blood. DNA from these bands of interest was eluted, reamplified by PCR, cloned and sequenced. Sequence analysis of 27 independent bacterial colonies allowed distribution of the different VH genes to seven B cell clones (A-G). Members of clone A were found in both joints and blood, clones B and C in one joint and blood, clone D in both joints, and clones E, F and G only in one joint. The VH regions were somatically mutated with characteristic patterns for the different clones. In conclusion, our findings confirm the systemic character of RA, because they show that not only expansion and affinity maturation of B cells occur in synovial membranes but antigen-specific B cells recirculate between different joints and blood.

Light chain variable (VL) sequences of rheumatoid factors (RF) in patients with primary Sjögren's syndrome (pSS): moderate contribution of somatic hypermutation

We have characterized and sequenced the variable (V) region genes of the light (L) chains of 10 immunoglobulin (IgM) rheumatoid factor (RF) monoclonal antibodies (MoAb) derived by the hybridoma/Epstein-Barr virus (EBV) technique from the peripheral blood of patients with primary Sjögren's syndrome (pSS). Six out of 10 RFs used lambda (lambda) L chains, while four RFs used kappa (kappa) L chains. Five out of the six lambda RFs were encoded by Vlambda3 gene segments, the sixth one was encoded by a Vlambda1 gene segment. This preferential utilization of the Vlambda3 family genes suggests selective expansion of the B cell in pSS. Three of the kappa RFs used Vkappa3 gene segments, while the fourth used a Vkappa2 gene segment. Half of the RFs were found as unmutated copies of their closest germline (GL) gene. Interestingly these RFs were previously shown to use heavy (H) chains in GL gene configuration. Three RFs have very few mutations (2-3) and only two RFs have substantial numbers of mutations (6 and 11). This also correlated with the number of mutations in the respective H chains. In contrast to RFs in normal and RA these results further suggest the somatic mutation to be of moderate importance in the generation of RF from the peripheral blood of pSS patients.