Detailed immunophenotypic characterization of different major and minor subsets of peripheral blood cells in patients with paroxysmal nocturnal hemoglobinuria

Immunophenotypic assessment of PNH clones in major and minor cell lineages in the peripheral blood of patients with paroxysmal nocturnal hemoglobinuria

BACKGROUND

Flow cytometric immunophenotyping is essential for the diagnosis of paroxysmal nocturnal hemoglobinuria (PNH). Most cases have easy to interpret flow cytometry profiles with red cells, neutrophils and monocytes showing complete deficiency of glycophosphatidylinositol (GPI) linked antigen expression. Some cases are more challenging to interpret due to the presence of multiple populations of PNH cells and variable levels of GPI antigen expression.

METHODS

We studied 46 known PNH patients, many with complex immunophenotypic profiles using a novel, single tube, multi-parameter 7-color immunophenotyping assay that allowed simultaneous detection and assessment of PNH clones within multiple lineages of peripheral blood leucocytes. Red cell PNH clones were also assessed in total and immature (CD71+) components by CD59 expression.

RESULTS

For individual patients, total PNH clones in each cell lineage were highly correlated. Monocytes, eosinophils and basophils showed the highest proportions of PNH cells. Red cell PNH clones were typically smaller than monocyte and neutrophil PNH clones. In most cases, PNH clones were detectable in minor leucocyte populations where multiple populations of PNH cells were present, variability in the proportions of type II and type III cells was seen across different cell lineages, even though total PNH clones remained similar.

CONCLUSIONS

This study shows that PNH patients with multiple PNH clones do not always display the same abnormality across all cell lineages routinely tested. There is no simple explanation for this but is likely due to a combination of complex molecular, genetic and biochemical dysfunction in different blood cell types.

Komplementinhibitoren: neue Therapeutika – neue Indikationen

Das Komplementsystem, ein klassisch transfusionsmedizinisches Thema, hat in den letzten Jahren in allen Bereichen der Medizin an Bedeutung gewonnen. Komplementinhibitoren werden aufgrund eines besseren Verständnisses der Pathophysiologie unterschiedlicher Erkrankungen in einem sich stetig erweiternden Krankheitsspektrum eingesetzt. Dieses reicht von typisch komplementassoziierten Erkrankungen wie der PNH (paroxysmale nächtliche Hämoglobinurie) bis hin zu akuten Krankheitsbildern mit einer Fehlregulation des Komplementsystems, wie COVID-19.

Diagnosis of paroxysmal nocturnal hemoglobinuria with flowcytometry panels including CD157: Data from the real world

BACKGROUND

Several studies have used CD157 in white blood cells with or without proaerolysin (fluorescein-labeled proaerolysin [FLAER])-based flow cytometry assays in the diagnosis of paroxysmal nocturnal hemoglobinuria (PNH).

METHODS

We designed a seven-color CD marker panel comprising FLAER, CD15, CD64, CD24, CD14, CD157, and CD45 to verify CD157's clinical applicability and diagnostic performance in a clinical setting.

RESULTS

A total of 356 samples were tested. These included 43 PNH-positive samples and 313 PNH-negative samples. PNH clones confirmed by the CD157/FLAER combination were almost identical in size to the clones detected by the CD24/CD14/FLAER combination, and the accuracy of the CD157/FLAER combination was 100% in granulocytes and 99.7% in monocytes. Substitution of FLAER with CD157 resulted in 1.9% and 3.5% false-positives in granulocytes and monocytes, respectively. The accuracy was 98.3% and 96.9% in granulocytes and monocytes, respectively. Moreover, the loss of CD157 expression in granulocytes and monocytes was commonly observed in non-PNH patients. Some monocytes in non-PNH patients had weak expression of CD14 but normal expression of FLAER. In this study, PNH clones in granulocytes were always lower than those in matched monocytes.

CONCLUSIONS

We performed the first prospective exploration of the clinical usefulness of FLAER and CD157 in simultaneously recognizing PNH clones in granulocytes and monocytes and verified the applicability of CD157 in substitute for both CD14 and CD24. In the conditions where FLAER is not available, substitution of FLAER with CD157 is acceptable for the identification of PNH clones under the premise of giving full attention to the potential for false-positives.

ICCS/ESCCA consensus guidelines to detect GPI-deficient cells in paroxysmal nocturnal hemoglobinuria (PNH) and related disorders part 3 - data analysis, reporting and case studies

Over the past several years, a diverse group of physicians and other laboratory scientists have developed various recommendations and guidelines regarding best practices for PNH testing. This manuscript is based on these previous recommendations as well as various other relevant publications of experts in the area of PNH testing. The goal is to provide flow cytometry laboratories with an updated consensus approach to analysis and reporting of PNH results and to address the most common analytical challenges for accurate reporting of this rare disease. A comprehensive case library is included in this section. © 2017 International Clinical Cytometry Society.

The presence of CD55- and/or CD59-deficient erythrocytic populations in patients with rheumatic diseases reflects an immune-mediated bone-marrow derived phenomenon

Background

Complement has the potential to provoke severe impairment to host tissues, as shown in autoimmune diseases where complement activation has been associated with diminished CD55 and/or CD59 expression on peripheral blood cell membranes. The aim of this study was to evaluate the presence of CD55- and/or CD59-deficient erythrocytic populations in patients with different rheumatic diseases and to investigate possible correlations with clinical or laboratory parameters.

Material/Methods

CD55 and CD59 expression was evaluated in erythrocytes of 113 patients with rheumatic diseases, 121 normal individuals, and 10 patients with paroxysmal nocturnal hemoglobinuria (PNH) using the Sephacryl gel microtyping system. Ham and sucrose tests were also performed.

Results

Interestingly, the majority of patients (104/113, 92%) demonstrated CD55- and/or CD59-deficient erythrocytes: 47 (41.6%) with concomitant deficiency of CD55 and CD59, 50 (44.2%) with isolated deficiency of CD55, and 6 (6.2%) with isolated deficiency of CD59. In normal individuals, only 2 (1%) had concomitant CD55/CD59 negativity and 3 (2%) had isolated CD55 or CD59 deficiency. All PNH patients exhibited simultaneous CD55/CD59 deficiency. Positive Ham and sucrose tests were found only in PNH patients. There was no association between the CD55- and/or CD59-deficient erythrocytes and hemocytopenias or undergoing treatment. However, CD55 expression significantly influenced hemoglobin values (F=6.092, p=0.015).

Conclusions

This study provides evidence supporting the presence of erythrocytes with CD55 and/or CD59 deficiency in patients with rheumatic diseases. Moreover, CD55 deficiency on red cells influences hemoglobin concentration. Further studies using molecular techniques will clarify the exact pathophysiological mechanisms of this deficiency.

Drugs that inhibit complement

The complement system is an important part of the innate immune system. Complement plays a crucial role in the pathophysiology of many disorders. Despite the pivotal role of the complement system, an approved targeted inhibitor of a complement factor became available only recently. Eculizumab is a humanized monoclonal antibody that inhibits complement factor C5. It is a targeted, disease modifying, treatment of paroxysmal nocturnal hemoglobinuria (PNH). It was approved be the US FDA and the European Commission in 2007. In this review we will update the experience with eculizumab in PNH and discuss potential use of eculizumab in other disorders (e.g. cold agglutinin disease; atypical HUS) and new approaches to complement inhibition with drugs other than eculizumab.

Paroxysmal nocturnal hemoglobinuria (PNH): higher sensitivity and validity in diagnosis and serial monitoring by flow cytometric analysis of reticulocytes

Flow cytometric analysis of GPI-anchored proteins (GPI-AP) is the gold standard for diagnosis of paroxysmal nocturnal hemoglobinuria (PNH). Due to therapy options and the relevance of GPI-deficient clones for prognosis in aplastic anaemia detection of PNH is gaining importance. However, no generally accepted standard has been established. This study analysed the usefulness of a flow cytometric panel with CD58, CD59 on reticulocytes and erythrocytes, CD24/CD66b and CD16, FLAER on granulocytes and CD14, and CD48 on monocytes. Actual cut-off (mean + 2 SD) for GPI-deficient cells was established in healthy blood donors. We studied 1,296 flow cytometric results of 803 patients. Serial monitoring was analysed during a median follow-up of 1,039 days in 155 patients. Of all, 22% and 48% of 155 follow-up patients. showed significant GPI-AP-deficiency at time of initial analyses. During follow-up in 9%, a new PNH diagnosis, and in 28%, a significant change of size or lineage involvement was demonstrated. Highly significant correlations for GPI-AP deficiency were found within one cell lineage (r² = 0.61–0.95, p < 0.0001) and between the different cell lineages (r² = 0.49–0.88, p < 0.0001). Especially for detection of small GPI-deficient populations, reticulocytes and monocytes proved to be sensitive diagnostic tools. Our data showed superiority of reticulocyte analyses compared with erythrocyte analyses due to transfusion and hemolysis independency especially in cases with small GPI-deficient populations. In conclusion, a screening panel of at least two different GPI-AP markers on granulocytes, erythrocytes, and reticulocytes provides a simple and rapid method to detect even small GPI-deficient populations. Among the markers in our panel, CD58 and CD59 on reticulocytes, CD24/66b, and eventually FLAER on granulocytes as well as CD14 on monocytes were most effective for flow cytometric diagnosis of GPI deficiency.

A closer look at paroxysmal nocturnal hemoglobinuria

Knowledge of the molecular mechanisms leading to the paroxysmal nocturnal hemoglobinuria (PNH) phenotypes has substantially increased in the past two decades. The associated intravascular hemolysis, hypercoagulablilty, and bone marrow failure result in a wide range of clinical sequlae. Although treatment has usually been symptomatic through several modalities and rarely curative through hematopoietic cell transplantation, recent development of the novel targeted therapeutic agent eculizumab has offered new promises for this highly morbid and fatal disease. This review summarizes current knowledge of the pathophysiology, diagnostic modalities, clinical implications, and treatment approaches of patients with PNH.

Ex vivo expansion and long-term hematopoietic reconstitution ability of sorted CD34+CD59+ cells from patients with paroxysmal nocturnal hemoglobinuria

Autologous bone marrow transplantation (ABMT) for paroxysmal nocturnal hemoglobinuria (PNH) remains difficult so far. To expand residual normal CD34(+)CD59(+) cells isolated from patients with PNH and observe the long-term hematopoietic reconstruction ability of the expanded cells both ex vivo and in vivo, CD34(+)CD59(+) cells from 13 PNH patients and CD34(+) cells from 11 normal controls were separated from bone marrow mononuclear cells first by immunomagnetic microbeads and then by flow cytometry autoclone sorting. The cells were then cultivated under different conditions. The long-term hematopoietic supporting ability of expanded CD34(+)CD59(+) cells was evaluated by long-term culture in semi-solid medium in vitro and long-term engraftment in irradiated severe combined immunodeficiency (SCID) mice in vivo. The best combination of hematopoietic growth factors for ex vivo expansion was SCF + IL-3 + IL-6 + FL + Tpo + Epo. The most suitable time for harvest was on day 7. CD34(+)CD59(+) PNH cells retained strong colony-forming capacity even after expansion. The survival rate, complete blood cell count recovery on day 90, and human CD45 expression in different organs were similar between the irradiated SCID mice transplanted with expanded CD34(+)CD59(+) PNH cells and those with normal CD34(+) cells (P > 0.05) both in primary and secondary transplantation. These data provided a new potential way of managing PNH with ABMT.