Synovial membrane immunohistology in early untreated juvenile idiopathic arthritis: differences between clinical subgroups

Abstract: Objective Juvenile idiopathic arthritis (JIA) consists of a heterogeneous group of inflammatory disorders, within which there are a number of clinical subgroups. Diagnosis and assignment to a particular subgroup can be problematical and more concise methods of subgroup classification are required. This study of the synovial membrane characterises the immunohistochemical features in early untreated, newly diagnosed JIA and compares findings with disease subgroup at 2 years.

Methods: 42 patients with newly diagnosed untreated JIA underwent synovial biopsy before the administration of steroids or disease-modifying antirheumatic drugs. Patients were classified as either polyarticular, persistent oligoarticular or extended-to-be oligoarticular. The location and semiquantitative analysis of T-cell subsets, B cells, macrophages and blood vessels were determined using immunohistochemistry.

Results: Synovial hyperplasia varied significantly between the three groups
(p<0.0001). There was a significant difference in the CD3 T-cell population between the three groups (p=0.004) and between the extended-to-be and persistent group (p=0.032). CD4 expression was significantly higher in the poly and extended-to-be oligo groups (p=0.002), again the extended-to-be group had more CD4 T cells than the persistent group (p=0.008). B-cell infiltrates were more marked in the polyarticular group and were significantly higher in the extended-to-be group compared with the persistent group (p=0.005). Vascularisation was more pronounced in the polyarticular and extended-to-be oligoarticular groups, the extended-to-be group had significantly more vascularisation than the persistent group (p=0.0002).

Conclusions: There are significant differences in the histomorphometric features of synovial tissue between patient subgroups. Immunohistological examination of synovial membrane biopsies may provide further insight into early disease processes in JIA.

Interaction of prothrombin with a phospholipid surface: evidence for a membrane-induced conformational change

Prothrombin interacts with phosphatidylserine containing platelet membranes via its N-terminal, gamma-carboxyglutamate (gla) residue-rich domain. Once bound it is cleaved to form the active protease, thrombin (factor IIa). Human prothrombin was cleaved with cathepsin G in the absence of calcium and magnesium ions. Under these conditions, the gla domain was removed. Phospholipid protected the protein from this proteolytic event, and this suggests that a conformational change may be induced by interaction with phospholipids. Binding of prothrombin to a surface containing 20% phosphatidylserine/80% phosphatidylcholine was detected by surface plasmon resonance, whereas no interaction with gla-domainless prothrombin was observed. Binding of intact prothrombin in the presence of calcium ions showed complex association kinetics, suggesting multiple modes of initial interaction with the surface. The kinetics of the dissociation phase could be fitted to a two-phase, exponential decay. This implies that there are at least two forms of the protein on the surface one of which dissociates tenfold more slowly than the other. Taken together, these data suggest that, on binding to a membrane surface, prothrombin undergoes a conformational change to a form which binds more tightly to the membrane.

Diabetic retinopathy: quantitative variation in capillary basement membrane thickening in arterial or venous environments

Diabetes mellitus was induced in male beagles by a single injection of an alloxan and streptozotocin cocktail and fasting blood sugar levels maintained between 15 and 20 mmol/l. Five years after induction of diabetes, three diabetic animals were sacrificed, together with sex and age-matched controls, and the retinas fixed for either transmission electron microscopy (TEM) or trypsin digestion. In TEM specimens, capillaries in close proximity to the major vessels were designated as either AE (arterial environment) or VE (venous environment) and the thickness of their basement membranes (BMs) measured using an image analyser based two dimensional morphometric analysis system. Results show that the BMs of retinal capillaries from the diabetic dogs were significantly thicker than those from control dogs. Furthermore, within the diabetic group the AE capillaries had thicker BMs than VE capillaries (p less than or equal to 0.05). The controls, however, showed no significant difference in BM thickness between AE and VE capillaries. Although many of the capillaries designated as AE or VE would actually have been derived from the opposite side of the circulation, with respect to BM thickness, they conformed to values of their specific group. The conclusion is that diabetic capillaries are more vulnerable to BM thickening in an arterial environment than in a venous environment.

Referral to an Extracorporeal Membrane Oxygenation Center and Mortality Among Patients With Severe 2009 Influenza A(H1N1)

Context Extracorporeal membrane oxygenation (ECMO) can support gas exchange in patients with severe acute respiratory distress syndrome (ARDS), but its role has remained controversial. ECMO was used to treat patients with ARDS during the 2009 influenza A(H1N1) pandemic.