Search PubMed⌕ Search

Biomedical subjects

J B Natvig

Publications and source records attributed to J B Natvig.

At least 19 recordsLinked to original sources
PubMed1995

Structural restriction in the heavy chain CDR3 of human rheumatoid factors.

We have compared the variable regions of 14 new IgM rheumatoid factors (RFs), produced in healthy human immunized donors (HIDs) with RFs originating from patients with rheumatoid arthritis (RA) and monoclonal Ig RFs (paraproteins or M-components, MC). Two groups with very restricted variable region structures were found. Twelve RFs (3 HID, 3 MC, and 6 RA) encoded by variable heavy (VH) chain germ-line genes with closest homology to DP-10 co-express the Kv325 variable light (VL) chain germ-line gene. These RFs have a remarkable restriction in the length (12-14 amino acids) and structure of the CDRH3. One HID RF has a CDRH3 only two amino acids different from the CDRH3 of a MC RF. Two sets of clonally related RFs, one from an RA patient and one from an HID, have CDRH3s that differ by only three amino acids. Five RFs (3 HID, 1 MC, and 1 RA) encoded by VH germ-line gene segments with closest homology to DP-54 all use the Kv328 VL germ-line gene combined to J kappa 1. Four are rearranged to the D21/9 D segment in the same reading frame, with CDRH3s of 16 to 17 amino acids. Three RFs (1 HID, 1 RA, and 1 MC) have CDRH3s differing by only three amino acids. The highly homologous V-regions in RFs from these two groups imply an initial selection to very similar, if not identical, epitopes. However, it remains to be seen whether somatic hypermutation alters the fine specificity of these autoantibodies.

Amino Acid Sequence↗
PubMed1995

V-gene repertoire and hypermutation of rheumatoid factors produced in rheumatoid synovial inflammation and immunized healthy donors.

We have compared RF from normal, immunized donors and RF derived from the synovial tissues of RA patients. We have found a difference in the preferential use of VL and VH gene families. In both conditions, RFs were found to have accumulated somatic mutations. However, there was a striking difference in the patterns of mutation. RFs from normals were characterized by a very low R:S ratio in the CDR1+2, considerably lower than seen among the RARFs. In addition, there was little increase in affinity with increasing numbers of mutations in a group of clonally related RFs from an immunized normal. This contrasts with RF from RA, where there is evidence of both affinity maturation and class switching. Together these data suggest that in healthy persons there is a controlling mechanism to limit the affinity of RF autoantibodies, and that this is lost in RA. The higher affinity of the RA-derived RF may be of significance in the pathology of the disease.

Antibody Affinity↗
PubMed1995

Structural characterization of peptides that bind synovial fluid antibodies from RA patients: a novel strategy for identification of disease-related epitopes using a random peptide library.

Phage epitope library technology has become a powerful tool for identifying determinants recognized by homogenous antibodies. Screening of human sera or fluids with random peptide phage libraries is a novel approach that can dissect common features at the amino acid level in individuals infected by the same etiological agent(s). In this study we have analyzed the specificity of antibodies in synovial fluids (SF) obtained from patients with rheumatoid arthritis (RA). We found that a high proportion of the peptides binding SF antibodies differ from those binding serum antibodies, suggesting that synovial B cells are expanded as a result of local antigen stimulation. When all the selected phages (enriched library) that bind the SF antibodies from a seropositive RA patient were further screened by the use of different SF antibodies with or without rheumatoid factor activity, we identified common SF antibody specificities (IRRSETPRA, RRRVRNSDT, PVSSTRGNM). Antibodies against these common specificities are also found in SF from other RA patients. Taken together, the present results open the possibility of defining the entire set of synovium antibody specificities and also common SF specificities between RA patients.

Amino Acid Sequence↗
PubMed1995

Peptide phage libraries can be an efficient tool for identifying antibody ligands for polyclonal antisera.

We have examined the potential of isolating ligands for polyclonal antibodies from a nanopeptide phage library. The library was screened with a rabbit polyclonal antiserum raised against a synthetic peptide (ALWFRNHFVFGGGTKVT). Following screening, the positive phages were tested in an ELISA for their reactivity with the antiserum. Phages that showed positive reactivity with the antiserum compared with a normal rabbit serum were selected and their displayed peptides were determined. Among the 36 random positive clones, 31 clones carried the sequence AVFGGGTKL, PFFGGGSRA or APTGGSKRT that have a significant homology to the immunizing peptide. Five positive phages displayed the ATNIFIEGT sequence, which has no obvious linear homology with either the other selected peptides or with the peptide used for immunization. In contrast to the control peptide, the immunizing peptide inhibited binding of the antiserum to the peptide-displaying phages in a dose-dependent manner, thus demonstrating the specificity of the interaction. Furthermore, the rabbit B cell response to the peptide was found to be limited and focused on its C-terminal. Taken together, our data demonstrate the potential of random peptide phage libraries for defining epitopes for polyclonal antisera as well as for investigation of the nature of B cell responses to any given antigen.

Amino Acid Sequence↗
PubMed1995

The identification of germinal centres and follicular dendritic cell networks in rheumatoid synovial tissue.

We document here the identification of germinal centres with dark and light zones, a follicular dendritic cell network and clonal expansion in the synovium of rheumatoid arthritis patients. Synovial tissue from 24 patients suffering from rheumatoid arthritis or the polyarticular form of juvenile rheumatoid arthritis were screened for the presence of lymphoid follicles. The synovial tissues of 14 patients contained follicles and four of these had germinal centres and a follicular dendritic cell network. There was a statistically significant association between follicles in the synovium and the presence of rheumatoid factor autoantibodies in the patients' serum indicating a link between local germinal centre formation and the presence of pathological rheumatoid factors. Nucleotide sequencing of monoclonal rheumatoid factors from one of the patients' synovial tissue which contained germinal centres clearly supports the possibility that these rheumatoid factors have gone through a germinal centre reaction. While rheumatoid factors from healthy immunized donors are regulated through a tolerization mechanism which selects against replacement mutations and does not allow affinity maturation, synovial rheumatoid factors seem to lack this tolerization mechanism. The formation of germinal centres where B cells affinity mature and expand at the central site of disease in rheumatoid arthritis may explain why rheumatoid factors in rheumatoid arthritis develop into auto-aggressive antibodies.

Adolescent↗
PubMed1995

Structural analysis of VH4-21 encoded human IgM allo- and autoantibodies against red blood cells.

We have sequenced the variable heavy chain regions of a number of VH4-21 encoded monoclonal IgM anti-Rh(D) antibodies produced in response to deliberate immunization. These were compared with the sequences of similarly encoded IgM anti-I cold agglutinins (CA) derived from patients with lympho-proliferative diseases. The anti-Rh(D) antibodies show evidence of clonal expansion and somatic diversification. Even though they are produced in response to an antigenic stimulus, they demonstrate limited hypermutation in the variable heavy chain (VH) segments and there is no evidence of selective pressure acting on the complementarity determining regions (CDRs). The CA demonstrate a higher rate of mutation and yet this results in a lower ratio of replacement to silent mutations (R:S) in the CDRs than seen in the anti-Rh(D) antibodies. It is not clear whether the different pattern of mutations seen in the CA is related to their auto-reactivity or their tumour origin. In both groups of antibodies the region encoded by the VH4-21 segment can be found in germline configuration at the amino-acid level indicating that other V-gene structures, i.e. light chains or CDRH3s, are crucial to the generation of either specificity. A role of the CDRH3 is indicated by the identification of a motif shared by four CAs and one Rh(D) antibody which also demonstrates CA activity independent of its anti-Rh(D) specificity. Amongst the anti-Rh(D) antibodies there seems to be an obligatory combination with VL having closest homology to the DPL16 germline segment indicating this as particularly important in generation anti-Rh(D) specificity.

Agglutinins↗
PubMed1994

Control of autoantibody affinity by selection against amino acid replacements in the complementarity-determining regions.

Rheumatoid factor (RF) autoantibodies can be produced in healthy individuals after infections or immunizations and thus escape normal tolerization mechanisms. It has not been clear whether such autoantibodies can undergo somatic hypermutation and affinity maturation similar to antibodies to exogenous antigens. We have investigated how these autoantibodies are regulated in normal individuals by analyzing the sequences of monoclonal IgM RFs obtained as hybridomas from donors after immunization. The variable regions undergo extensive hypermutation, but in contrast to antibodies against exogenous antigens, there is a strong selection against mutations that result in replacement of amino acids in the hypervariable, or complementarity-determining, regions. Furthermore, we found no increase in affinity of these RFs with the accumulation of mutations. This suggests that high-affinity variants are tolerized during the hypermutation process and there is a peripheral mechanism operating on certain autoreactive B cells that, while not deleting or anergizing all autoreactive cells, prevents the generation of high-affinity autoantibodies. Comparison of RFs by using the VH1 DP-10 heavy chain variable region segment from both normal individuals and rheumatoid arthritis (RA) patients suggests that RF from RA patients may not be subject to such a controlling mechanism.

Antibody Affinity↗
PubMed1994

Variable region gene usage of human monoclonal rheumatoid factors derived from healthy donors following immunization.

A study was performed to compare the use of immunoglobulin V gene segments by rheumatoid factors (RF) produced in physiological responses following a defined antigenic stimulus, with RF produced in rheumatoid arthritis (RA) and RF produced as monoclonal (M)-components in certain lympho-proliferative diseases. A panel of 46 monoclonal RF was produced, using hybridoma techniques, from healthy individuals following immunization with foreign antigens (mis-matched red blood cells). A panel of previously characterized monoclonal RF from RA synovial tissues was extended to a total of 24 and included in the study. The variable heavy (VH) and variable light (VL) chain gene families used by these RF were determined using idiotypic markers and polymerase chain reaction amplification with VH-specific primers. The frequencies of expression of the various gene families was compared between the two groups, and compared with the published expression frequencies seen amongst M-component RF. The majority (87%) of RF from healthy donors were found with light chains using V gene segments of the V chi 3 family, in conjunction with VH gene segments belonging to the VH1, VH3 and VH4 families. The over-expression of V chi 3, together with the distribution of VH families, demonstrates close similarities with RF found as M-components in lympho-proliferative diseases. In contrast, RF from RA patients showed a predominant use of VH3 gene segments (82%) and an unbiased expression of V chi 3 segments (29% of the chi light chains). These data suggest that RF found as M-components are representative of RF used in normal physiological responses, but have undergone neoplastic or other transformation. RF found in the synovial tissue of RA patients appear to be driven by different mechanisms than RF seen in physiological responses in healthy individuals.

Arthritis, Rheumatoid↗
PubMed1994

Different cytokine production profiles of gamma delta T cell clones: relation to inflammatory arthritis.

This study was performed to investigate whether gamma delta T cells could also be divided into subsets, identified by a cytokine profile, as described for alpha beta T helper (Th) cell subsets. Cytokine production was studied in 22 gamma delta T cell clones obtained from the synovial fluid and peripheral blood of one patient with inflammatory arthritis and compared to that of 26 alpha beta T cell clones of the same and different patients. Interferon-gamma (IFN-gamma) was produced by 18 (82%) and interleukin-4 (IL-4) by 17 (77%) out of 22 gamma delta T cell clones, respectively. In contrast, IL-10 was not produced, except at very low level in one case. The mean levels of IL-4 were lower for clones derived from synovial fluid. When considering the production of IFN-gamma as an indicator of Th1 and that of IL-4 as an indicator of Th2, respectively, the most common pattern was a gamma delta Th1-like pattern, with the combination of high levels of IFN-gamma and low levels of IL-4. This pattern was found in V delta 1+ clones, all from synovial fluid. Additional patterns were also observed: a mixed, probably gamma delta Th0-like pattern with a more balanced production of both IFN-gamma and IL-4; a gamma delta Th1 pattern with the production of IFN-gamma alone; a gamma delta Th2 pattern with the production of IL-4 alone. These three patterns were also seen in blood gamma delta T cells which were all V delta 2, indicating that these patterns were independent of the V delta phenotype. gamma delta T cell clones produced lower levels of IFN-gamma (p = 0.001) and higher levels of IL-4 than alpha beta clones (p < 0.02). These differences in cytokine production between alpha beta and gamma delta subsets and within these subsets may contribute to their respective role in chronic inflammation.

Adolescent↗
PubMed1994

Characterization of naturally occurring autoantibodies against tumour necrosis factor-alpha (TNF-alpha): in vitro function and precise epitope mapping by phage epitope library.

Naturally occurring autoantibodies against cytokines exist in the sera of patients with autoimmune diseases as well as in the sera of normal individuals. We report here that affinity-purified autoantibodies against human TNF-alpha from one rheumatoid arthritis (RA) patient inhibited the cytotoxic effect of TNF-alpha on the mouse fibrosarcoma cell line WEHI 164, by 50%. In an attempt to predict the autoantibodies' recognition site on TNF-alpha protein we screened a random nanopeptide phage library with the affinity-purified TNF-alpha autoantibodies. Among 63 random selected clones, 46 clones carried the sequence ASSLLASSP, NSSPYLNTK or PQSPGSSFP. Frequency analysis of the relative occurrence of the 20 amino acids in the nanopeptides displayed by 50 random bacteriophages picked before selection and 63 after selection to bind to TNF-alpha autoantibodies indicated that proline (P < 0.0003) and serine (P < 0.04) are involved in the binding of the autoantibodies to the phages. Furthermore, we demonstrated that three synthetic peptides (ASSLLASSP, NSSPYLNTK and PPLKPVIDE) displayed by the selected phages reduced the binding of the autoantibodies to TNF-alpha protein by 50%. Interestingly, the sera of mice (BALB/c) immunized with phages displaying ASSLLASSP and NSSPYLNTK peptide showed an anti-TNF-alpha response as detected by ELISA. This response was not found in mice immunized with the wild type phage. Thus, the recombinant phages selected from the phage libraries could be used as carrier for immunization, and therefore as a tool for vaccine development. This work sets the stage for experiments designed to isolate ligands for protective antibodies.

Antibody Specificity↗
PubMed1994

The binding of synovial tissue-derived human monoclonal immunoglobulin M rheumatoid factor to immunoglobulin G preparations of differing galactose content.

There are several sites on IgG Fc that have been reported to be the epitopes for binding rheumatoid factors (RF). It is now established that there are alterations in the oligosaccharides on IgG from patients with rheumatoid arthritis and it has been suggested that these changes may enhance immune complex and cryoglobulin formation. We have used a series of IgG preparations differing in their content of oligosaccharide chains lacking galactose from 18 to 86% to determine whether changes in sugar content affect the binding of rheumatoid factor. Five of 16 monoclonal rheumatoid factors prepared from synovial tissue, from patients with juvenile or adult rheumatoid arthritis, bound better to IgG which was deficient in galactose. Six of the 16 rheumatoid factors from the same patients bound independently of the galactose content. Four of the 16 rheumatoid factors could not be absolutely grouped in this manner but seemed to demonstrate a preference for agalactosyl IgG. One rheumatoid factor bound better to fully galactosylated IgG. There was an association between enhanced binding to galactose-deficient IgG and monoreactivity and a very strong association between the functional affinity of the rheumatoid factors and the dependent binding.

Antibodies, Anti-Idiotypic↗
PubMed1994

Three new cross-reacting idiotopes as markers for the products of two distinct human VH3 genes expressed in the early repertoire.

This article describes characterization of three new cross-reacting idiotopes, as recognized by mouse MoAbs, on human antibodies utilizing VH3 genes that are expressed in the early repertoire. Two of the mouse MoAbs (3H7 and 3H1) were raised against a human MoAb utilizing the DP47 (VH26) VH3 gene, whilst the third (7B4) was raised against a DP46 (GLSJ2) gene product. Evidence for the anti-idiotypic specificity of the mouse MoAbs was provided by their reactivity with the immunizing IgM, but not with Fc mu, and by their specific inhibition of the binding between each immunizing antibody and its antigen. The three anti-idiotypic MoAbs were shown to be VH-specific reagents by the independence of their reactivity upon the L-chain type, or the antigenic specificity of the human MoAbs tested. Specificity of each mouse MoAb for VH3 gene-products was demonstrated by its sole cross-reactivity with VH3 proteins. Each anti-Id had a different reactivity pattern with a panel of MoAbs utilizing different VH3 genes. By relating the VH sequences of the tested VH3 proteins to their germline counterparts, 3H7 and 3H1 appeared to be specific for DP47-encoded proteins, although 3H1 had weak cross-reactivities with a few other VH3 gene-products. 7B4 appeared to be specific for antibodies utilizing DP46-related genes. Both 3H7 and 3H1 were also completely different to B6 and D12, two previously described MoAbs that also recognize VH3 proteins. Although 7B4 was similar to B6 and D12 in its binding to DP46-related gene products, B6 and D12 additionally recognized non DP46-related proteins and were thus different to 7B4.

Animals↗
PubMed1994

Human monoclonal rheumatoid factors: incidence of cross-reactions with tissue components and correlation with VH gene usage.

Human monoclonal antibodies with rheumatoid factor (RF) activity, derived from lymphocytes from the synovial tissue of rheumatoid arthritis (RA) patients and the peripheral blood of healthy individuals were examined for cross-reactivity with tissue and cellular antigens. The majority of IgM RF from RA patients (68%) showed reactivity with at least one component, and were frequently multispecific. A very significantly smaller proportion (28%) of the RF derived from healthy individuals demonstrated reactivities against tissue/cellular antigens (P = 0.004). RF from RA patients most commonly reacted with gastric glands (61%), nuclei (50%) and smooth muscle (50%), whereas RF from healthy donors most commonly reacted with gastric glands (20%), smooth muscle (16%), endothelium (16%) and glomeruli (16%). The most striking difference between the two groups was the reactivity with nuclear components, demonstrated by 50% of the RA RF, but by none of the healthy donor RF. As the two groups of antibodies share the same specificity for IgG Fc, but show differences in variable region segment usage, we investigated the relationship between VH gene usage and tissue/cell cross-reactivity using these antibodies and anti-blood group antibodies. Antibodies using VH3 or VH4 gene segments showed a very significantly greater frequency of tissue/cell reactions than those using VH1 (P = 0.0095 and 0.0004 respectively).

Antibodies, Monoclonal↗
PubMed1993

Mapping studies reveal unique epitopes on IgG recognized by rheumatoid arthritis-derived monoclonal rheumatoid factors.

We have used chimeric IgG antibodies and their genetically engineered variants prepared by a combination of site-directed mutagenesis and exon exchange to define the structure(s) on IgG recognized by monoclonal rheumatoid factor (RF) autoantibodies from rheumatoid arthritis (RA) patients. Nineteen RF produced by EBV-transformed cell lines from the synovium or blood of RA patients were analyzed. Their binding patterns differ significantly from those seen with RF obtained from patients with Waldenstrom's macroglobulinemia (WMac). Half of the RA-derived RF bound IgG1, 2, and 4, but not 3 (Ga specificity), the common pattern in WMac. However, heterogeneity in fine specificity within the Ga reactivity pattern was observed. Moreover, seven others bound all four IgG subclasses, a pattern observed for only one WMac-derived RF from a patient who also had RA. Three RF had subclass specificities unlike any observed with WMac-derived RF. Most RA-derived RF bound IgG at a discontinuous epitope comprised of residues from both the CH2 and CH3 H chain constant regions. However, unlike any WMac-derived RF, one RA-derived RF bound IgG in CH2, another in CH3, and a third at an undetermined site outside of the CH2-CH3 interface. Some RA-derived RF bound aglycosylated IgG4 less well than glycosylated IgG4, suggesting that the carbohydrate moiety was important in establishing their binding epitope in CH2. These studies demonstrate that the repertoire of RF expressed by RA patients contains some unique binding specificities for IgG epitopes not found among our panel of WMac-derived RF. Our results therefore call into question whether WMac-derived RF with their limited diversity are appropriate models for disease-related RF. In addition, RF with their multiple specificities can serve as probes of antibody structure.

Animals↗
PubMed1993

Identification of new B cell epitopes in the sera of rheumatoid arthritis patients using a random nanopeptide phage library.

A random nanopeptide phage library was used to screen a pool of immunoglobulin fractions obtained from rheumatoid arthritis (RA) patients. After three rounds of panning, random individual phages were selected by their capacity to react with individual sera from RA patients. By sequencing the inserts corresponding to the peptides displayed on the surface of the phages, we found that phages displaying particular peptides were overrepresented in the selected libraries. The peptides displayed by these phages were: pep1 = Ala-Asp-Gly-Gly-Ala-Gln-Gly-Thr-Ala; pep2 = Pro-Gly-Pro-Ser-Arg-Ala-His-Phe-Leu; pep3 = Leu-Ser-Ser-Arg-Glu-Pro-Gln-Ala-Arg; pep4 = Arg-Leu-Thr-Arg-Glu-Leu-Tyr-Ala-Gln and pep5 = Tyr-Thr-Gln-Lys-His-Gln-Ala. The percentage of sera positive for pep1 was higher in RA patients as compared to the normal adults (p < 0.0004) and the reacting antibody was mainly of IgG isotype. The specificity of binding to the phage displaying pep1 was confirmed by competition experiments using both isolated phages and a synthetic peptide. Interestingly, a mutated phage displaying only Ala-Asp-Gln-Gly-Thr-Ala had no significant reactivity with the sera, indicating that the amino acids (Gly-Gly-Ala) of pep1 are the vital for the binding. Taken together this study demonstrates that it is possible to select specific ligands from a random phage library using sera from RA patients. In addition, this approach could be useful for identifying peptide antigens that might be part of causitive agents in autoimmune diseases.

Amino Acid Sequence↗
PubMed1993

Human monoclonal IgG rheumatoid factors from the synovial tissue of patients with rheumatoid arthritis.

We have established IgG rheumatoid factor (RF)-secreting hybridoma cell lines from the synovial tissues of two patients (TS and SJ) with rheumatoid arthritis (RA) and one (KL) with the polyarticular form of juvenile rheumatoid arthritis (JRA). The IgG RF bind human and rabbit IgG and all except one form intracellular complement-fixing complexes indicative of a self-association process. The possibility of IgG RF for self association and immune complex formation is a feature thought to be important for the inflammatory processes in RA. Of the IgG RF-secreting cell lines established, three clones from patient SJ and one from patient KL are of the IgG1 kappa isotype while five clones from patient TS are of the IgG2 lambda isotype.

Antibody Specificity↗