ObjectivesA previously identified signal transduction and activator of transcription-3 (STAT3) target-enriched gene signature in circulating CD4+ T cells of patients with early rheumatoid arthritis (RA) was prominent in autoantibody-negative individuals. Here, interleukin (IL)-6-mediated STAT signalling was investigated in circulating lymphocytes of an independent early arthritis patient cohort, seeking further insight into RA pathogenesis and biomarkers of potential clinical utility.MethodsConstitutive and IL-6-induced expression of phosphorylated STAT1 (pSTAT1) and pSTAT3 was determined in T and B cells using Phosflow cytometric analysis in patients with RA and controls. Contemporaneous levels of serum cytokines were measured by immunoassay. Induced gene expression was measured in cultured CD4+T cells by quantitative real-time PCR.ResultsAmong circulating lymphocytes of 187 patients with early arthritis, constitutive pSTAT3 correlated with serum IL-6 levels maximally in CD4+ T cells. Increased constitutive pSTAT3, but not pSTAT1, was observed in circulating CD4+ T cells of patients with early anticitrullinated peptide autoantibody (ACPA)-negative RA compared with disease controls, and these levels decreased alongside markers of disease activity with IL-6R-targeted treatment. Among patients presenting with seronegative undifferentiated arthritis (UA) the ratio of constitutive pSTAT3:pSTAT1 in CD4+ T cells contributed substantially to an algorithm for predicting progression to classifiable RA during a median of 20 months follow-up (area under receiver operator characteristic curve=0.84; p<0.001).ConclusionsOur findings support a particular role for IL-6-driven CD4+ T cell activation via STAT3 during the induction of RA, particularly as a feature of ACPA-negative disease. CD4+ T cell pSTAT measurements show promise as biomarkers of UA–RA progression and now require independent validation.

Aims-To evaluate an immunohistological stain for complement component C9 as a method of detecting early myocardial infarction and to compare this with (1) an enzyme histochemical method and (2) conventional histological staining. Methods-(1) Eight hearts taken at necropsy were stained using the nitroblue tetrazolium/phenazine methosulphate method and an immunohistological stain for C9. (2) Twenty five hearts from cases of suspected or confirmed myocardial infarction and 25 from cases without conventional evidence of infarction were stained for C9 and by haematoxylin and eosin. Results-(I) The histochemical method indicated myocardial necrosis in five hearts and the C9 method in seven, all of which had clinical evidence of myocardial damage or a reason for it. The histochemical method required fresh myocardium, was difficult to use and was difficult to interpret. (2) Of 25 hearts with suspected or confirmed infarction, 24 were stained by the C9 method. Staining with haematoxylin and eosin showed infarction in 16 of these, all with infarcts at least 24 hours old; the other eight had clinical evidence of infarction less than 24 hours old. Tne heart not stained by C9 was from a patient who, on review, had no evidence ofinfarction. Ofthe 25 control hearts, none had infarction on staining with haematoxylin and eosin, but three were stained by the C9 method. These three were from patients with septicaemia or another reason for myocardial damage. Conclusions-The immunohistological method for C9 is a simple, reliable and sensitive method for the detection of early myocardial necrosis that could be used on formalin fixed, paraffin wax embedded necropsy material. This had advantages over a histochemical method and conventional staining with haematoxylin and eosin. (Jr Clin Pathol 1996;49:34-37) Keywords: C9, myocardial infarction.Recent myocardial infarction can be impossible to detect either by direct examination at necropsy or using conventional stains on histological sections. Histochemical techniques can show early infarction, but these are difficult to interpret and rarely used. A method of detection of infarction that could be used on formalin fixed, paraffin wax embedded sections would be of great value.Complement component C9, part of the C5b-9 membrane attack complex of complement, is a reliable marker of complement deposition and can be detected immunohistologically on formalin fixed, paraffin wax embedded sections of renal biopsy specimens.1 This membrane attack complex has also been found in necrotic skeletal muscle fibres2 and in infarcted myocardium.3 We wished to see whether the immunohistological stain for C9 could be used as a routine method for demonstrating recent myocardial infarction, by comparing it with an established histochemical technique, the nitroblue tetrazolium/phenazine methosulphate reaction,4 and against conventional staining with haematoxylin and eosin. Methods HISTOCHEMICAL STUDYTransverse slices, about 1-2 cm thick, were taken from the left ventricle of eight patients at necro...