IgM rheumatoid factor elaboration by blood, bone marrow, and synovial mononuclear cells in patients with rheumatoid arthritis

IgM and IgA rheumatoid factors purified from rheumatoid arthritis sera boost the Fc receptor- and complement-dependent effector functions of the disease-specific anti-citrullinated protein autoantibodies

Rheumatoid factors (RF) and the disease-specific anti-citrullinated protein autoantibodies (ACPA) coexist in the joints of rheumatoid arthritis (RA) patients where they probably contribute to synovitis. We investigated the influence of IgM and IgA RF on the FcR- and complement-dependent effects of ACPA immune complexes (ACPA-IC). When stimulated by ACPA-IC formed in the presence of IgM RF or IgA RF fractions purified from RA serum pools, M-CSF-generated macrophages skewed their cytokine response toward inflammation, with increases in the TNF-α/IL-10 ratio and in IL-6 and IL-8 secretion, and decreases in the IL-1Ra/IL-1β ratio. In the IgM RF-mediated amplification of the inflammatory response of macrophages, the participation of an IgM receptor was excluded, notably by showing that they did not express any established receptor for IgM. Rather, this amplification depended on the IgM RF-mediated recruitment of more IgG into the ACPA-IC. However, the macrophages expressed FcαRI and blocking its interaction with IgA inhibited the IgA RF-mediated amplification of TNF-α secretion induced by ACPA-IC, showing its major implication in the effects of RF of the IgA class. LPS further amplified the TNF-α response of macrophages to RF-containing ACPA-IC. Lastly, the presence of IgM or IgA RF increased the capacity of ACPA-IC to activate the complement cascade. Therefore, specifically using autoantibodies from RA patients, the strong FcR-mediated or complement-dependent pathogenic potential of IC including both ACPA and IgM or IgA RF was established. Simultaneous FcR triggering by these RF-containing ACPA-IC and TLR4 ligation possibly makes a major contribution to RA synovitis.

IgM rheumatoid factor amplifies the inflammatory response of macrophages induced by the rheumatoid arthritis-specific immune complexes containing anticitrullinated protein antibodies

OBJECTIVES

Anticitrullinated protein antibodies (ACPA) are specifically associated with rheumatoid arthritis (RA) and produced in inflamed synovial membranes where citrullinated fibrin, their antigenic target, is abundant. We showed that immune complexes containing IgG ACPA (ACPA-IC) induce FcγR-mediated tumour necrosis factor (TNF)-α secretion in macrophages. Since IgM rheumatoid factor (RF), an autoantibody directed to the Fc fragment of IgG, is also produced and concentrated in the rheumatoid synovial tissue, we evaluated its influence on macrophage stimulation by ACPA-IC.

METHODS

With monocyte-derived macrophages from more than 40 healthy individuals and different human IgM cryoglobulins with RF activity, using a previously developed human in vitro model, we evaluated the effect of the incorporation of IgM RF into ACPA-IC.

RESULTS

IgM RF induced an important amplification of the TNF-α secretion. This effect was not observed in monocytes and depended on an increase in the number of IgG-engaged FcγR. It extended to the secretion of interleukin (IL)-1β and IL-6, was paralleled by IL-8 secretion and was not associated with overwhelming secretion of IL-10 or IL-1Ra. Moreover, the RF-induced increased proinflammatory bioactivity of the cytokine response to ACPA-IC was confirmed by an enhanced, not entirely TNF-dependent, capacity of the secreted cytokine cocktail to prompt IL-6 secretion by RA synoviocytes.

CONCLUSIONS

By showing that it can greatly enhance the proinflammatory cytokine response induced in macrophages by the RA-specific ACPA-IC, these results highlight a previously undescribed, FcγR-dependent strong proinflammatory potential of IgM RF. They clarify the pathophysiological link between the presence of ACPA and IgM RF, and RA severity.

Polymorphism of the human immunoglobulin heavy chain locus in rheumatoid arthritis

The genetic origin of Rheumatoid Arthritis (RA) is largely unknown. The purpose of this investigation was to assess the potential genetically determined involvement of the immunoglobulin (Ig) heavy chain variable region (VH) locus in the pathogenesis of RA. We tested the hypothesis of whether there is a genetic linkage between a structural abnormality of the VH gene complex and autoantibody hyperproduction in RA. We used restriction endonuclease generated polymorphism with human VH gene-family-specific probes to examine genomic DNA from a RA family and from unrelated RA patients from both the Tunisian and the European populations. The use of DNA samples from these ethnic origins permitted a further evaluation of the polymorphism of the human VH locus. While we found that the polymorphism of the VH locus was lower in the Tunisian population, we could not detect a restriction site polymorphism pattern restricted to RA. Together, our results do not support the involvement of major abnormalities of the Ig VH locus as a primary source in the development of RA.

Accelerated generation of CD14+ monocyte-lineage cells from the bone marrow of rheumatoid arthritis patients

OBJECTIVE

To examine the capacity of bone marrow progenitor cells to generate CD14+ cells, in order to assess the role of bone marrow in the pathogenesis of rheumatoid arthritis (RA).

METHODS

CD14- cells purified from bone marrow specimens of 11 patients with active RA and 8 control patients (osteoarthritis or trauma) were cultured in the presence or absence of granulocyte-macrophage colony-stimulating factor (GM-CSF; 100 pg/ml). After incubation for various lengths of time, the cells were analyzed by flow cytometry for expression of CD14 and HLA-DR.

RESULTS

The spontaneous generation of CD14+ cells from bone marrow CD14- progenitor cells was accelerated in RA patients compared with control patients. Moreover, the expression of HLA-DR on the bone marrow-derived CD14+ cells was also accelerated in RA patients compared with controls. GM-CSF significantly enhanced the generation of CD14+ cells, as well as the expression of HLA-DR, on CD14+ cells of control patients, but not those of RA patients. GM-CSF levels in the culture supernatants of bone marrow CD14- cells were not significantly different between RA patients and control patients (undetectable in most cases).

CONCLUSION

These observations strongly support the hypothesis that the accelerated generation of CD14+ cells from bone marrow progenitor cells and the accelerated maturation of such CD14+ cells into HLA-DR+ cells play an important role in the pathogenesis of RA. Moreover, the data suggest a functional alteration of RA bone marrow CD14- cells in their responsiveness to GM-CSF.

Selective induction of IgM rheumatoid factors by CD14+ monocyte-lineage cells generated from bone marrow of patients with rheumatoid arthritis

OBJECTIVE

To determine the capacity of CD14+ monocyte-lineage cells induced from bone marrow of rheumatoid arthritis (RA) patients to stimulate the production of IgM rheumatoid factor (IgM-RF), in order to explore the functional abnormalities of CD14+ cells and gain insight into the mechanism of selective synthesis of IgM-RF in RA.

METHODS

CD14+ cells were induced by granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulation of CD14- cells purified from bone marrow cells obtained from 6 RA patients and 6 osteoarthritis (OA) patients. The production of IgM and IgM-RF was induced by stimulating B cells from normal healthy individuals with immobilized anti-CD3-activated autologous CD4+ T cells. The effects of CD14+ cells on the proportion of IgM-RF to total IgM produced by the normal B cells were assessed.

RESULTS

CD14+ cells induced by GM-CSF stimulation of bone marrow CD14- cells from the 6 RA patients significantly enhanced the proportion of IgM-RF to total IgM produced by anti-CD3-activated CD4+ T cell-stimulated normal B cells (P < 0.05), whereas GM-CSF-induced CD14+ cells from the bone marrow of the 6 OA patients did not significantly affect IgM-RF production. CD14+ cells induced by GM-CSF obtained from different sites in the same RA patient on different occasions consistently enhanced the proportion of IgM-RF to IgM produced by B cells from different normal subjects.

CONCLUSION

These results indicate that abnormal CD14+ monocytes stimulate RF-producing B cells to be ready to be activated by the signals delivered through noncognate T-B interactions with anti-CD3-activated T helper cells. Moreover, the data suggest that the accelerated generation of such functionally abnormal CD14+ cells from bone marrow precursors might play an important role in the pathogenesis of RA.

Nucleotide sequence analysis of rheumatoid factors and polyreactive antibodies derived from patients with rheumatoid arthritis reveals diverse use of VH and VL gene segments and extensive variability in CDR-3

The heavy and light chain nucleotide sequences of 17 monoreactive and polyreactive rheumatoid factors largely derived from the inflamed synovial tissue of two patients with rheumatoid arthritis are described. Some of these sequences have been the subject of a previous report from our laboratories. Additionally, a few rheumatoid factors from the peripheral blood of patients with systemic lupus erythematosus and Sjogren's syndrome as well as a normal individual are included. A review of our previous results as well as the new data provided within this paper lead to the following major conclusions: (1) Rheumatoid factors and polyreactive antibodies derive from a diverse array of VH and VL gene segments; (2) While many rheumatoid factors and polyreactive antibodies are direct or nearly direct copies of germline genes, some show clear evidence of somatic mutation; (3) The CDR3 of all of these antibodies is extraordinarily diverse in length and composition. Certain 'restrictions' do appear in this very large sample: (a) the polyreactive antibodies are exclusively lambda, and (b) there seems to be a preponderance of a particular subset of VH3 genes beyond that one would expect based on random utilization.

The complete nucleotide sequences of the heavy chain variable regions of six monospecific rheumatoid factors derived from Epstein-Barr virus-transformed B cells isolated from the synovial tissue of patients with rheumatoid arthritis. Further evidence that some autoantibodies are unmutated copies of germ line genes

Structural studies of human monoclonal rheumatoid factors (RF) derived from patients with monoclonal gammapathies have revealed a restriction in the usage of heavy and light chain variable regions. These studies have suggested that germline genes with little if any somatic mutation can generate RF specificity. However, there is no information presently available regarding the primary structure and genetic origin of RF in rheumatoid arthritis. In this study, we have isolated and sequenced the VH regions of six monoclonal RF derived from the synovial membranes of two patients with rheumatoid arthritis and one with the juvenile polyarticular form of the disease. We found the same VH families as previously reported among monoclonal paraproteins with RF activity. However, our sample was diverse regarding the VH, DH, and JH gene segments used. Among VHI RF there was conservation in the length of CDRIII as well as restriction in the amino acid generated at the V-D junction, as opposed to VHIII RF and non-RF VHI molecules that are highly heterogeneous in these two aspects. We also found that different JH gene segments may contribute to RF specificity. The VH, DH, and JH elements of one RF in our study all had clearly identifiable germline counterparts. This RF displays a nearly germline configuration throughout its entire heavy chain and represents another example of an autoantibody encoded by one of the VH gene segments from the preimmune fetal repertoire.

Human mononuclear cells and neutral proteinases. III. Neutral proteinases and rheumatoid arthritis: monocytes as a source of cathepsin G and proteinase potentiation of IgM rheumatoid factor elaboration

We have been interested in contributions of certain cells and mediators to synovial inflammation rheumatoid arthritis (RA). The present studies were designed to determine (1) whether monocytes contained the neutral proteinase cathepsin G and (2) if neutral proteinase could induce or potentiate cellular IgM rheumatoid factor (RF) production. Monocyte-rich and monocyte-poor populations were isolated by Ficoll-Hypaque density sedimentation followed by glass adherence, and cellular lysates were obtained by repetitive freezing and thawing as we have reported for neutrophil-derived neutral proteinase. Cathepsin G was quantified immunochemically by an enzyme-linked immunoassay (ELISA) we developed utilizing commercially available anti-cathepsin G antibodies. Mononuclear and B-cell-enriched cell cultures were prepared by standard methods and IgM RF measured by our ELISA. Cell-derived lysates from monocyte-enriched populations (84 +/- 3% monocytes, less than 1% neutrophils) contained considerably greater amounts of measurable cathepsin G (OD280 = 0.393 +/- 0.153) than lysates from equal numbers of monocyte (15 +/- 2% monocytes, less than 1% neutrophils)-depleted cells (OD280 = 0.071 +/- 0.038; P less than 0.05). Eighteen patients with RA and three normal individuals did not have consistently increased cellular elaboration of Ig or IgM RF in vitro in response to proteinase (trypsin) stimulation; however, patients manifested 80% potentiation by trypsin of pokeweed-stimulated cellular IgM RF production in vitro (pokeweed-stimulated IgM RF 137 +/- 53 ng/ml, pokeweed/trypsin-induced IgM RF 246 +/- 100 ng/ml; P less than 0.02), changes being most striking for those patients seropositive by latex fixation test (84% increase, P less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Complete protein sequences of the variable regions of the cloned heavy and light chains of a human anti-cytomegalovirus antibody reveal a striking similarity to human monoclonal rheumatoid factors of the Wa idiotypic family

The complete amino acid and nucleotide sequences of the variable regions of the heavy and light polypeptide chains of a human neutralizing IgGl anti-cytomegalovirus (CMV) antibody reveal a striking homology to IgM rheumatoid factors (RFs) of the Wa idiotypic family. The anti-CMV antibody and Wa RFs have in common VKIIIb, JKl, and VHIa gene segments but use different DH and JH gene segments. The anti-CMV antibody does not have RF activity and does not express the Wa idiotype. The Wa RFs do not have anti-CMV activity. A subset of Wa RFs, however, and the anti-CMV antibody do share several idiotypes on the VHIa and VKIIIb polypeptides. Since there are major differences in the antigen binding characteristics and some of the other expressed idiotypes, these data suggest that the D and J region amino acids are crucial to such specificities. Although the use of such highly homologous gene segments in different immune responses is well-documented in murine systems, these data represent the first such example in the human.