Epstein-Barr virus etiology in rheumatoid synovitis

The etiology of rheumatoid arthritis (RA) has remained unknown, although it has been investigated and speculated that both genetic and environmental components contribute to the cause of this disease. Epstein-Barr virus (EBV) has been a strong candidate about for over 25 years as environmental infectious agent(s). There are many circumstantial evidence for association between EBV and RA, but definite evidence is wanting. In present article, we review an increase circumstantial proof which has been investigated so far and demonstrate direct evidence for the presence of EBV in inflamed synovial cells in patients with RA and discuss on the recent finding of signaling lymphocytic-activation molecule (SLAM)-associated protein (SAP), which opened a new approach to understand on impaired function of cytotoxic T cell for EBV in patients with RA.     

Eicosanoid production by density-defined human peritoneal macrophages during inflammation

Density-defined macrophages isolated from fluids of patients with liver cirrhosis mainly generated the 5-lipoxygenase products leukotriene B₄ (LTB₄, 16%) and 5-hydroxy-eicosatetraenoic acid (5-HETE, 24%) and the cyclooxygenase products 12-hydroxyheptadecatrienoic acid (HHT, 22%) and thromboxane B₂ (TXB₂, 18%). The synthesis of eicosanoids was linear with the maturity of the macrophage subpopulations, suggesting that eicosanoid production is increased inin-vivo activated macrophages.

     

The morphogenesis of chronic synovitis in rheumatoid arthritis]

The synovial sheath obtained in synovectomy in 35 patients with rheumatic- and rheumatic-visceral forms of rheumatoid arthritis was studied histochemically and immunomorphologically. At early stages of exacerbation of the pathological process in the synovial tissue there were revealed predominantly catabolic processes: an increased permeability of vessels; mucoid oedema; fibrinoid changes in the subintimal layer. Further development of the disease was characterized by predominance of anabolic processes with proliferation of synoviocytes, subintimal histiocytes, productive vasculites, massive lymphoid-plasmocytic infiltration, diffuse, or in the form of lymphoid follicles. Using the immunofluorescent technique the authors revealed luminescence of the rheumatoid factor and gamma=globulin in plasmatic cells, extracellularly, and more rarely in macrophages. Pronounced immunological changes in the synovial sheath in the active course of rheumatoid arthritis were accompanied by a high level of metabolic processes and an intensive phagocytic reaction in synoviocytes and subintimal histiocytes. In observations with a low activity of rheumatoid arthritis the synovial tissue was characterized by low levels of enzymes of oxidative metabolism and hydrolysis, emptying of the capillary bed, processes of sclerosis, hyalinosis, amyloidosis.     

Eicosanoid production by density-defined human peritoneal macrophages during inflammation

Density-defined macrophages isolated from fluids of patients with liver cirrhosis mainly generated the 5-lipoxygenase products leukotriene B₄ (LTB₄, 16%) and 5-hydroxy-eicosatetraenoic acid (5-HETE, 24%) and the cyclooxygenase products 12-hydroxyheptadecatrienoic acid (HHT, 22%) and thromboxane B₂ (TXB₂, 18%). The synthesis of eicosanoids was linear with the maturity of the macrophage subpopulations, suggesting that eicosanoid production is increased inin-vivo activated macrophages.     

Systematic microanatomical analysis of CXCL13 and CCL21 in situ production and progressive lymphoid organization in rheumatoid synovitis

CXCL13 and CCL21 have been functionally implicated in lymphoid tissue organization both in the upstream phases of lymphoid tissue embryogenesis and in ectopic lymphoid neogenesis in transgenic mice. Here, we analyzed the relationship between CXCL13 and CCL21 production and lymphoid tissue organization in rheumatoid synovitis as a model of a naturally occurring ectopic lymphoneogenesis. Through systematic analysis of mRNA and protein expression, we defined the microanatomical relationship between CXCL13 and CCL21 in progressive aggregational and structural phases of synovial inflammatory infiltrate. We provide the first direct in situ evidence that production of CXCL13 and CCL21 (rather than simply protein binding) is associated with inflammatory lymphoid tissue formation and development with the demonstration, in organized aggregates, of a secondary lymphoid organ-like compartmentalization and vascular association. Notably, the presence of CXCL13 and CCL21 (protein and mRNA) was also demonstrated in non-organized clusters and minor aggregational stages, providing evidence that their induction can take place independently and possibly upstream of T-B compartmentalization, CD21(+) follicular dendritic cell network differentiation and germinal center formation. Our data support the concept that, under inflammatory conditions, CXCL13 and CCL21 participate in lymphoid tissue microanatomical organization, attempting to recapitulate, in an aberrant lymphoid neogenetic process, their homeostatic and morphogenetic physiologic functions.     

Immune complexes in rheumatoid synovitis: a mixed staining immunofluorescence study

Complexes of IgG—rheumatoid factor (RF) and IgG—β_1C were demonstrated in the synovial membrane obtained from patients with rheumatoid arthritis (RA) by a mixed immunofluorescence method that shows simultaneously the two components of the complex.

IgG—RF was found only in the synovia of cases with circulating RF, while IgG—β_1C deposits could be detected in both seropositive and seronegative cases.

These findings are discussed in connection with the pathogenesis of rheumatoid synovitis in the light of the immune complex pathogenetic mechanism.

     

Eicosanoid production by the mucosa in inflammatory bowel disease after 5-ASA treatment

Eicosanoids were measured in biopsies of colonic mucosa from five patients with active ulcerative colitis before and after a four weeks of treatment with 5-amino-salicylic acid (5-ASA). Eicosanoid formation was determined after the addition of¹⁴C-arachidonic acid and stimulation with calcium ionophore A23187. 5-ASA given intra-rectally caused a non-selective suppression of prostanoids, leukotrienes and hydroxyeicosatetraenoic acids. Changes in arachidonic acid metabolism after 5-ASA treatment were not always reflected in changes in inflammation score.

     

Immunohistochemical demonstration of CD23 expression on lymphocytes in rheumatoid synovitis.

The leucocyte antigen CD23 is expressed by B lymphocytes following activation by a number of stimuli and functions as an IgE receptor, and in its soluble form, as a putative B cell growth factor. The expression of CD23 on the surface of lymphocytes in paraffin wax sections of synovial biopsy specimens was studied using a novel mouse monoclonal antibody, BU38. Specimens were investigated from nine cases of rheumatoid arthritis, six cases of osteoarthritis, and eight cases of chronic inflammation in articular and non-articular tissues. CD23 was expressed on a high proportion of lymphocytes in all forms of chronic inflammation and was not specific for rheumatoid arthritis. It may be a characteristic feature of any chronic inflammatory response. As CD23 was found on the surface of lymphocytes in many cases of these arthritides, sCD23 in serum or synovial fluid may yet prove a useful marker for the severity of the inflammatory infiltrate.     

Do mast cells intervene in the vasoproliferative process of the rheumatoid synovitis?

On the basis of these evidences: a) the role played by heparin in the promotion of angiogenetic processes; b) the isolation of an angiogenetic factor in the synovial fluid from patients with rheumatoid arthritis; c) the significant increase of mast cells in the synovial membrane of the same patients, we suggest the possibility that the vasoproliferative processes in the course of rheumatoid arthritis may be mediated by heparin contained in the secretory granules of mast cells and released during the inflammatory process in response to numerous and heterogeneous stimuli.     

Eicosanoid production in nonparenchymal liver cells isolated from rats infused with E. coli endotoxin

Continuous i.v. infusion of a nonlethal dose of Escherichia coli endotoxin induced an early (3-h) accumulation of neutrophils in the rat liver followed by a later (30-h) greater extravasation of mononuclear phagocytes (MNP). These inflammatory cells, recovered together by centrifugal elutriation, were analyzed for their potential capacity to metabolize [1-14C]-AA. Ca2+ ionophore A23187 (5 microM) stimulated the release of [1-14C]-AA from PC and PI both in cells from saline- and ET-infused rats, the latter showing a higher capacity to further metabolize AA to eicosanoids. LTB4 and 5-HETE were the major metabolites accumulated in cells from rats infused with ET for 3 h, while PGD2 played the main role in cells from saline-infused rats. This could reflect [1-14C]-AA metabolism by PMNP and Kupffer cells, respectively. By 30 h of ET-infusion, a shift from PGD2 to PGE2 release was observed. These results suggest that eicosanoids released by nonparenchymal cells (i.e., Kupffer and endothelial cells) and PMNP in the liver of ET-infused rats may alter the normal intercellular information flow between parenchymal and nonparenchymal cells, contributing to the severe impairment in liver function and metabolism during endotoxicosis and sepsis.     

Morphological and molecular pathology of the B cell response in synovitis of rheumatoid arthritis

The synovitis of rheumatoid arthritis (RA) was long regarded merely as an unspecific chronic inflammatory process of minor diagnostic value and therefore did not play a major role in the understanding of the pathogenesis of RA. It is only in recent years, along with the observation that T and B cells are expanded oligoclonally in synovial tissue and that B cells are able to undergo a local germinal center (GC) reaction, that the synovial tissue has come to be regarded as a site of specific immune processes. The analysis of the immunoglobulin (Ig) gene repertoire had great impact on the understanding of B cell response in lymphatic organs and was subsequently applied to B cells from RA patients. The analyses of the variable (V) regions of the Ig heavy (H) and light (lambda) chains suggested that an antigen specific activation and differentiation of B cells into plasma cells (Plc) takes place in the chronically inflamed synovial tissue of patients with RA. It seems that in a subset of RA patients the synovial tissue develops into an ectopic lymphoid tissue that supports a local GC reaction. Ectopic GC are characteristic of RA; however, they are in general absent from synovitis of osteoarthritis (OA). Here the accumulation of Plc follows a different mechanism. Highly mutated VH genes suggest that in OA memory B cells migrate into the synovial tissue with subsequent differentiation into Plc but without further V gene diversification. Therefore in synovitis two patterns of B cell activation can be differentiated: the maturative and the accumulative type. These two patterns are not definitely disease linked. The maturative type is only found in RA whereas the accumulative type occurs in both diseases. Clinically RA is defined via serum antibodies to the constant region of Ig, so-called rheumatoid factor. However, the spectrum of autoreactive B cells in RA patients is wide and is based on the study of antibody specificities in serum, in synovial fluid and B cell lines derived from peripheral blood, bone marrow, synovial fluid and synovial tissue. These analyses defined non-organ-specific and organ-specific antigens. One can reasonably assume that the disease is far too complex to be explained by only a single antigen. There is a whole combination of antigens acting in a multistep manner that is responsible for RA pathogenesis. It can be hypothesized that chronic synovitis, which is the underlying mechanism of joint destruction, follows a three-step process: (a) initiation, (b) destruction, and (c) perpetuation. The characterization of antigens driving the local synovial B cell maturation and accumulation could lead to an understanding of the process perpetuating the disease. Identification of arthritogenic antigens may yield new avenues for diagnostics and immunotherapy but also a new approach for prevention by vaccines with antigens probably defined by synovial B cell reactivity.     

Eicosanoid production by peritoneal and splenic macrophages in mice depleted of bone marrow by 89Sr

Previous studies showed that the prostaglandin-forming macrophages (M phi) induced in the spleens of CBA/J mice by intraperitoneal administration of Corynebacterium parvum (CP) could not be demonstrated following the depletion of bone marrow and blood monocytes with 89Sr. The present study compares prostaglandin E2 (PGE2), leukotriene C4 (LTC4), and LTB4 release by splenic and resident peritoneal M phi in 89Sr-treated mice and 88Sr controls following in vivo CP and in vitro incubation with zymosan, calcium ionophore A23187, or phorbol ester (PMA). Intraperitoneal administration of CP resulted in the appearance of PGE2- and LTB4-releasing M phi in the spleens of control but not 89Sr mice. The incorporation and quantitative distribution of 3H-arachidonic acid into membrane lipids, however, were comparable in test and control mice. Neither zymosan nor any of the other stimulatory agents was able to effect significant release of PGE2 in vitro. No release of LTC4 by splenic M phi was detectable under experimental or control conditions. In contrast, the capacity of resident peritoneal M phi to release PGE2, LTC4, and LTB4 was apparently unaffected by 89Sr-induced bone marrow and monocyte depletion with virtually no demonstrable elicitation. Resident peritoneal M phi removed after CP in such mice showed a dramatic decrease in PGE2 release when incubated in vitro with zymosan, A23187, or PMA. These results, taken with earlier findings, demonstrate characteristically different phenotypic expression of metabolism of certain eicosanoids by splenic M phi from the spleen and the peritoneal cavity and suggest in addition that the induction of PGE2-synthesizing M phi in the spleen by CP is dependent on either an immigrant cell originating in the bone marrow or a regulatory agent derived from a bone marrow cell.     

T cell receptor delta diversity of freshly isolated T lymphocytes in rheumatoid synovitis.

In some patients with rheumatoid synovitis the distribution of V delta gene families used by freshly isolated T lymphocytes from the synovial fluid and peripheral blood is different: peripheral blood T lymphocytes preferentially use the V delta 2 gene segment, whereas the majority of synovial fluid T lymphocytes use the V delta 1. The antigenic diversity of T cell receptor gamma/delta is mainly dependent upon base sequences in the V-J junction. In the present study we investigated whether the synovial fluid T lymphocytes expressing the V delta 1 gene segment were derived from a polyclonal or monoclonal expansion. The sequences encoding the V-J junctions of 11 cDNA clones derived from the synovium of two patients with chronic arthritis were determined. Our data demonstrate that the V delta 1 cDNA clones have different V-J junction sequences. This indicates that the V delta 1-expressing T cells found in the synovial compartment are polyclonally expanded.