What is the role of complement in bystander hemolysis? Old concept, new insights

INTRODUCTION

Bystander hemolysis occurs when antigen-negative red blood cells (RBCs) are lysed by the complement system. Many clinical entities including passenger lymphocyte syndrome, hyperhemolysis following blood transfusion, and paroxysmal nocturnal hemoglobinuria are complicated by bystander hemolysis.

AREAS COVERED

The review provides data about the role of the complement system in the pathogenesis of bystander hemolysis. Moreover, future perspectives on the understanding and management of this syndrome are described.

EXPERT OPINION

Complement system can be activated via classical, alternative, and lectin pathways. Classical pathway activation is mediated by antigen-antibody (autoantibodies and alloantibodies against autologous RBCs, infectious agents) complexes. Alternative pathway initiation is triggered by heme, RBC microvesicles, and endothelial injury that is a result of intravascular hemolysis. Thus, C5b is formed, binds with C6-C9 compomers, and MAC (C5b-9) is formulated in bystander RBCs membranes, leading to cell lysis. Intravascular hemolysis, results in activation of the alternative pathway, establishing a vicious cycle between complement activation and bystander hemolysis. C5 inhibitors have been used effectively in patients with hyperhemolysis syndrome and other entities characterized by bystander hemolysis.

Endocrinopathies in Hemoglobinopathies: What Is the Role of Iron?

Hemoglobinopathies, including β-thalassemia and sickle cell disease (SCD), are common genetic blood disorders. Endocrine disorders are frequent manifestations of organ damage observed mainly in patients with β-thalassemia and rarely in SCD. Iron overload, oxidative stress-induced cellular damage, chronic anemia, and HCV infection contribute to the development of endocrinopathies in β-thalassemia. The above factors, combined with vaso-occlusive events and microcirculation defects, are crucial for endocrine dysfunction in SCD patients. These endocrinopathies include diabetes mellitus, hypothyroidism, parathyroid dysfunction, gonadal and growth failure, osteoporosis, and adrenal insufficiency, affecting the quality of life of these patients. Thus, we aim to provide current knowledge and data about the epidemiology, pathogenesis, diagnosis, and management of endocrine disorders in β-thalassemia and SCD. We conducted a comprehensive review of the literature and examined the available data, mostly using the PubMed and Medline search engines for original articles. In the era of precision medicine, more studies investigating the potential role of genetic modifiers in the development of endocrinopathies in hemoglobinopathies are essential.

Risk Factors, Prevalence, and Outcomes of Invasive Fungal Disease Post Hematopoietic Cell Transplantation and Cellular Therapies: A Retrospective Monocenter Real-Life Analysis

(1) Background: Autologous, allogeneic hematopoietic cell transplantation (HCT) and other cellular therapies, including CAR T cell and gene therapy, constitute a cornerstone in the management of various benign and malignant hematological disorders. Invasive fungal infections (IFD) remain a significant cause of morbidity and mortality in HCT recipients. Therefore, we investigated the prevalence and risk factors of IFD following HCT and other cellular therapies in an era of novel antifungal prophylaxis. (2) Methods: In this study, we retrospectively enrolled adult HCT recipients who were treated at our JACIE-accredited center according to standard operating procedures over the last decade (2013-2022). (3) Results: 950 patients who received cellular therapies were studied. None of the 19 CAR T cell and neither of the two gene therapy recipients developed IFD whereas 3/456 autologous HCT recipients who suffered from primary refractory/relapsed lymphomas presented with probable IFD. Overall, 11 patients who received allogeneic HCT experienced probable IFD, possible IFD was found in 31/473, and IFD was proven in 10/473. A second IFD episode was present in three patients. Four-year OS was significantly lower in proven compared to probable IFD (p = 0.041) and was independently associated with HCT-CI (p = 0.040) and chronic GVHD (p = 0.045). (4) Conclusions: In this real-world cohort, the prevalence of proven and probable IFD in an era of novel antifungal prophylaxis was found to be relatively low. However, IFDs were associated with poor outcomes for patients who received allogeneic HCT.

CNS Border-Associated Macrophages: Ontogeny and Potential Implication in Disease

Being immune privileged, the central nervous system (CNS) is constituted by unique parenchymal and non-parenchymal tissue-resident macrophages, namely, microglia and border-associated macrophages (BAMs), respectively. BAMs are found in the choroid plexus, meningeal and perivascular spaces, playing critical roles in maintaining CNS homeostasis while being phenotypically and functionally distinct from microglial cells. Although the ontogeny of microglia has been largely determined, BAMs need comparable scrutiny as they have been recently discovered and have not been thoroughly explored. Newly developed techniques have transformed our understanding of BAMs, revealing their cellular heterogeneity and diversity. Recent data showed that BAMs also originate from yolk sac progenitors instead of bone marrow-derived monocytes, highlighting the absolute need to further investigate their repopulation pattern in adult CNS. Shedding light on the molecular cues and drivers orchestrating BAM generation is essential for delineating their cellular identity. BAMs are receiving more attention since they are gradually incorporated into neurodegenerative and neuroinflammatory disease evaluations. The present review provides insights towards the current understanding regarding the ontogeny of BAMs and their involvement in CNS diseases, paving their way into targeted therapeutic strategies and precision medicine.

Knowledge, attitudes, and perceptions regarding COVID-19 outbreak in Greece in September 2020: a cross-sectional web-based survey

BACKGROUND

Decreasing the transmission rate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is related to people's knowledge, attitudes, and perceptions towards the novel coronavirus. Our study investigated the above factors aiming at pandemic's successful management.

METHODS

A web-based survey was conducted among the general Greek population from 11^th September to 7^th October 2020 after institutional ethics approval, using a non-probability, convenience sampling method. The survey consisted of socio-demographic, knowledge, attitude, and perception questions towards coronavirus disease 2019 (COVID-19). Statistical analyses conducted were appropriate according to the type of variable and the research question.

RESULTS

We collected a total of 9,309 questionnaires with a completeness rate estimated at 98.3 %. The median knowledge score regarding COVID-19 was 72.7 %, exhibiting variation depending on socio-demographic subgroups. Individuals were better informed about coronavirus modes of transmission (86.4 %). The acceptance of the COVID-19 vaccine among the general population was 25.9 %, while 43 % of participants remained undecided about being vaccinated. A significant part of the respondents experienced a health issue for which they had to visit a hospital, but they did not do so due to the fear of possible infection by SARS-CoV-2.

CONCLUSIONS

Our findings suggest a moderately high level of knowledge in the Greek population towards COVID-19 at the study time. Educational programs, health actions, and vaccination campaigns are essential for filling knowledge gaps in particular demographic groups, such as the low educated and over 65 years old people. Interventions may be needed for the National Healthcare System to recover citizens' confidence. Measures strengthening individual wellbeing and social solidarity during the pandemic should also be of high priority. HIPPOKRATIA 2021, 25 (1):15-21.

Neuroendocrine carcinoma as a rare cause of jejunal intussusception in an adult. Management and literature review

Intussusception of the small bowel is an uncommon condition, with the majority of cases being observed during infancy. A number of points are responsible, with benign and malignant lesions of the small intestine being the most common. Herein, we present the case of a 75-year-old male patient with vague abdominal pain and black stool during defecation, who underwent surgery due to jejunal intussusception. Pathology report demonstrated a neuroendocrine carcinoma as the underlying cause for his condition, with no additional metastases during the initial diagnosis. Although a conservative approach for management of intussusception is viable, the possibility of gastric outlet obstruction and the presence of malignancy as the primary point usually lead to urgent surgery. In the case of malignancy, adjuvant chemotherapy or additional symptomatic therapy with close follow-up may be required depending on tumor's grade and aggressiveness.