IgE deposition in normal skin of patients with rheumatoid arthritis in relation to clinical and laboratory findings

B-cell involvement in the pathogenesis of RA-is there a contribution of the sympathetic nervous system?

The pathogenesis of rheumatoid arthritis (RA), the most common rheumatic disease, is still an unsolved puzzle. For many years, T-cells were the main focus of research, but recently, the B-cell drew more and more attention not least, due to the observation in humans that the anti-CD20 antibody Retuximab, which selectively depletes subsets of B-cells, lessens disease symptoms. A second novel approach to understand pathomechanisms that contribute to the development and progression of arthritis focuses on the sympathetic nervous system, which is known to moderate the function of immune cells, e.g., the B-cell, and therefore, is tied into a complex neuroimmune network that influences the course of the disease. This review first discusses current research that shows the significance of B-cells in the pathogenesis of RA. It then gives a short review of knowledge regarding the role of the sympathetic nervous system (1) in RA pathogenesis and (2) in modulating B-cell responses. Finally, the hypothesis is introduced that the sympathetic nervous system via modulating B-cell function, e.g., antibody production, influences the development and progression of RA.

B lymphocytes and humoral immune responses in rheumatoid arthritis

Although the etiology of rheumatoid arthritis (RA) remains unknown at present, major evidence implicates humoral immune mechanisms in the pathophysiology of this disease. The primary lesions occur in the synovium and are characterized by immunological activation and chronic inflammation. Activated B cells and plasma cells secrete antibodies including rheumatoid factors and anticollagen antibodies. These antibodies give rise to immune complex formation and activation of the inflammatory cascade. There is no evidence that rheumatoid factor secreting B cells act as antigen presenting cells and present immune complex to T cells, leading to perpetuation of the inflammatory response.

Experimental arthritis in rats induced by intra-articular injection of IgE aggregates: evidence for arthritogenic role of complexed IgE

An experimental arthritis model in the rat was used to study the arthritogenic potential of complexed IgE. IgE aggregates were produced in vitro by cross linking monoclonal rat IgE by dimethyl suberimidate and were injected into the knee joints. Animals which had not been injected and animals injected with phosphate buffered saline served as controls. The concentration of histamine in tissues, diffusion into the joint of bovine serum albumin labelled with iodine-125 injected intravenously, and the histology of the joints were studied. There was a significant decrease in the concentration of histamine in synovial tissue 8 and 24 hours after the injection of the IgE aggregates. A decreased number of stainable mast cells were found 8, 24, and 48 hours after exposure. A moderate hyperplasia of the synovial lining layer was also noted. These results provide further evidence for the arthritogenic potential of complexed IgE, especially in the initiation of arthritis through activation of mast cells.

Activation of inflammatory cells by immune complexes containing IgE in serum and synovial fluid of patients with rheumatoid arthritis: a study using flow cytometric analysis

Neutrophil and monocyte activation by immune complexes containing IgE from serum and synovial fluid of patients with rheumatoid arthritis is reported. Activation of the inflammatory cells was measured by stimulation of the respiratory burst with production of intracellular hydrogen peroxide. Generation of hydrogen peroxide was analysed by a flow cytometric method, using the fluorochrome dichlorofluorescein. The technique was modified to allow measurement of cell activation of both neutrophils and monocytes by immune complexes in suspension. Ten of 14 polyethylene glycol precipitates from serum of patients with rheumatoid arthritis and 10/16 synovial fluids of these patients could activate neutrophils. A positive relation was found between the activation of neutrophils and the total concentration of immune complexes, the presence of IgG, and the presence of IgE in the immune complexes. Activation of monocytes was also shown, but to a lesser extent (8/14 rheumatoid serum samples and 8/16 rheumatoid synovial fluids activated monocytes). There was a weak correlation between the concentration of IgE immune complexes and the intensity of fluorescence measured in the monocytes.

Cholesterol crystals and IgE-containing immune complexes in rheumatoid pericarditis

A 72-year-old rheumatoid arthritis patient is described presenting with acute dyspnoea and peripheral oedema. A pericardial effusion with signs of tamponade was diagnosed. Examination of the pericardial fluid revealed the presence of cholesterol crystals and IgE-containing immune complexes. The significance of these findings in the differential diagnosis of pericardial disease is discussed.

IgE-containing immune complexes in synovial fluid of patients with rheumatoid arthritis

The prevalence and composition of IgE-containing immune complexes in paired synovial fluid and serum of 42 patients with classical or definite rheumatoid arthritis were studied. IgE-containing immune complexes were found in 15/42 synovial fluids; 15 sera were also positive. The correlation between serum and synovial fluid complexed IgE levels was high (r = 0.77). The mean ratio of synovial fluid/serum levels was 1.96, i.e. significantly higher than 0.33, the synovial fluid/serum ratio for alpha-2-macroglobulin (molecular weight 820 kD), which was taken as high molecular weight control protein (p less than 0.0001). Apart from IgE in immune complex form, monomeric IgE was also significantly higher in synovial fluid compared to serum (ratio = 2.94). Other constituents which could be found in the immune complexes, i.e. anti-IgE antibodies, rheumatoid factors and anticollagen antibodies, were also higher in synovial fluid than predicted. Our results suggest intra-articular production of IgE-containing complexes in the synovial fluid, in addition to possible exudation of the complexes from the serum. These findings provide further evidence for the role of IgE-containing immune complexes in rheumatoid synovitis.

Role of IgM-rheumatoid factor interference in the determination of total serum IgE and IgE-containing circulating immune complexes

IgM-rheumatoid factor (RF) interference in the determination of total serum IgE and IgE-containing circulating immune complexes (IgE-CIC) was studied by inhibition experiments in vitro comparing a new ELISA technique free of IgM-RF interference with more widely used RIA methods. It was shown that a considerable overestimation of the IgE content in CIC can exist when high levels of IgM-RF are present in the same serum. The clinical part of this study revealed a dramatic fall in prevalence of IgE-CIC in patients with rheumatoid arthritis (RA) with the ELISA technique, compared with the more conventional RIA method (respectively 1/20 compared to 12/20 positive for IgE-CIC). In these patients, there was a good correlation between the level of IgM-RF and the amount of IgE detected in the CIC by the RIA method (r = 0.87) whereas the RF-interference free ELISA method showed no correlation between these two parameters (r = 0.06). Total serum IgE determination with a solid phase RIA was also influenced by IgM-RF interference, whereas the PRIST method was not affected by the presence of IgM-RF. In conclusion, in patients with rheumatic diseases, IgE-assays using polyclonal rabbit or sheep anti-IgE antibodies are not appropriate and monoclonal anti-IgE antibodies that have been proved not to interfere with IgM-RF should be advocated.

Neutrophil activation by IgE-containing circulating immune complexes of patients with connective tissue diseases

In an earlier study, we reported IgE-containing circulating immune complexes (CICs) in 66.6% of the patients with rheumatoid arthritis who were studied, especially in those with extra-articular manifestations. The present study was undertaken to examine the possible role of these immune complexes in inflammatory cell activation. Twelve patients with classic or definite rheumatoid arthritis, two with primary Sjögren's syndrome, and three patients with systemic lupus erythematosus were studied. Of these 17 patients, 10 were IgE-containing CIC positive, and seven patients were IgE-containing CIC negative. Polyethylene glycol-precipitated IgE-containing CICs and IgG-containing CICs of these patients were coated on plastic wells and incubated with suspensions of neutrophils. As a parameter of cell activation, superoxide release (SOR) was measured by cytochrome C reduction in the supernatant after 30, 60, and 90 minutes. There was a significant SOR up to 38% of the zymosan control when IgE-containing CICs were incubated with neutrophils. Furthermore, there was a significant correlation between the level of IgE-containing CICs and the amount of SOR, but not between the level of IgG-containing CICs and the amount of SOR. These results suggest a possible role for IgE-containing CICs in the activation of inflammatory cells in connective tissue diseases.