Since publication in 2010 of the International Clinical Cytometry Society (ICCS) Consensus Guidelines for detection of Paroxysmal nocturnal hemoglobinuria (PNH) by flow cytometery, a great deal of work has been performed to develop, optimize, and validate a number of high-sensitivity assays to detect PNH phenotypes in both red blood cells (RBCs) and white blood cells (WBCs, neutrophils, and monocytes). This section (Part 2) of the updated ICCS PNH Consensus Guidelines will focus on specific instrument setup for these PNH assays, the identification and proper testing of appropriate antibody conjugates and combinations therof, and basic assay design. V C 2017 International Clinical Cytometry Society

Objectives A retrospective population‐based study to determine the incidence and prevalence of patients with the rare blood disease paroxysmal nocturnal haemoglobinuria (PNH). Methods All patients were identified by flow cytometric detection of blood cells deficient in glycosylphosphatidylinositol (GPI) linked proteins at a single diagnostic reference laboratory that serves the Yorkshire based, Haematological Malignancy Research Network (HMRN) with a population of 3.8 million. Results One hundred and ninety‐seven patients with detectable PNH clones at a level of >0.01% in at least two lineages of cells (neutrophils, monocytes and/or red cells) were identified over a 15‐year period (2004‐2018). Of these, 88% had aplastic anaemia (AA), 8% classical PNH and 3% myelodysplastic syndrome. The overall incidence rate was estimated at 0.35 cases per 100 000 people per year. This equates to 220 cases newly diagnosed in the United Kingdom each year. The overall prevalence rate was 3.81 per 100 000, this equates to an estimated 2400 prevalent cases in the UK. The overall and relative 5‐year survival rates were 72% and 82.7%, respectively. Conclusions This study showed that classical haemolytic PNH is a rare disease and represents only a small proportion overall of patients with detectable PNH cells, the majority of which have aplastic anaemia.

SummaryThe interaction of chemokines and their receptors directs lymphocyte migration, and is involved in the distribution and organization of lymphocytes within lymphoid tissues. We reasoned that abnormal chemokine receptor expression might give rise to defects of lymphocyte migration into and within lymphoid tissues, and consequently be associated with defective antibody production in primary antibody deficiencies. In this study, we have investigated the expression of chemokine receptors CXCR4, CXCR5 and CCR7 on lymphocyte subpopulations (naive and memory B cells; CD4 + and CD8 + T cells) in a cohort of patients with primary antibody deficiency (n = 23), and compared these with a group of healthy controls (n = 19). We show that there were significant differences in both the proportions of lymphocytes expressing, and the levels of expression of, specific chemokine receptors on individual lymphocyte subpopulations between patients and controls. Furthermore, these changes appeared more pronounced in patients with more severe antibody deficiency. These data support the hypothesis that abnormal lymphocyte trafficking may be involved in the pathogenesis of primary antibody deficiencies.

No abstract

Advancing age and chronic health conditions, significant risk factors for severe COVID-19, are associated with a pro-inflammatory state, termed inflamm-aging. CXCR6+ T cells are known to traffic to the lung and have been reported to increase with age. The ligand of CXCR6, CXCL16, is constitutively expressed in the lung and upregulated during inflammatory responses and the CXCR6/CXCL16 axis is associated with severe lung disease and pneumonia. Genome-wide association studies have also recently identified 3p21.31, encompassing the CXCR6 gene, as a susceptibility locus for severe COVID-19. We assessed numbers T cells expressing the chemokine receptor CXCR6 and plasma levels of CXCL16, in control and COVID-19 patients. Results demonstrated that circulating CD8+CXCR6+ T cells were significantly elevated with advancing age, yet virtually absent in patients with severe COVID-19. Peripheral levels of CXCL16 were significantly upregulated in severe COVID-19 patients compared to either mild COVID-19 patients or SARS-CoV-2 negative controls. This study supports a significant role of the CXCR6/CXCL16 axis in the immunopathogenesis of severe COVID-19.

No abstract

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematological disorder, characterized by complement‐mediated intravascular hemolysis and thrombosis. The increased incidence of PNH‐driven thrombosis is still poorly understood, but unlike other thrombotic disorders, is thought to largely occur through complement‐mediated mechanisms. Treatment with a C5 inhibitor, eculizumab, has been shown to significantly reduce the number of thromboembolic events in these patients. Based on previously described links between changes in fibrin clot structure and thrombosis in other disorders, our aim was to investigate clot structure as a possible mechanism of thrombosis in patients with PNH and the anti‐thrombotic effects of eculizumab treatment on clot structure. Clot structure, fibrinogen levels and thrombin generation were examined in plasma samples from 82 patients from the National PNH Service in Leeds, UK. Untreated PNH patients were found to have increased levels of fibrinogen and thrombin generation, with subsequent prothrombotic changes in clot structure. No link was found between increasing disease severity and fibrinogen levels, thrombin generation, clot formation or structure. However, eculizumab treated patients showed decreased fibrinogen levels, thrombin generation and clot density, with increasing time spent on treatment augmenting these antithrombotic effects. These data suggest that PNH patients have a prothrombotic clot phenotype due to increased fibrinogen levels and thrombin generation, and that the antithrombotic effects of eculizumab are, in‐part, due to reductions in fibrinogen and thrombin generation with downstream effects on clot structure.

The case of a 6-year-old boy who presented with acute post-streptococcal glomerulonephritis is reported. C3 levels and complement alternative pathway activity remained low for at least 10 months after presentation, before returning to normal. There was no evidence of other renal disease. This case highlights that hypocomplementaemia in acute post-streptococcal glomerulonephritis may persist for several months, and that prolonged hypocomplementaemia does not exclude this diagnosis.