Macrophages tightly control the production and clearance of red blood cells (RBC). During steady state hematopoiesis, approximately 1010 RBC are produced per hour within erythroblastic islands in humans. In these erythroblastic islands, resident bone marrow macrophages provide erythroblasts with interactions that are essential for erythroid development. New evidence suggests that not only under homeostasis but also under stress conditions, macrophages play an important role in promoting erythropoiesis. Once RBC have matured, these cells remain in circulation for about 120 days. At the end of their life span, RBC are cleared by macrophages residing in the spleen and the liver. Current theories about the removal of senescent RBC and the essential role of macrophages will be discussed as well as the role of macrophages in facilitating the removal of damaged cellular content from the RBC. In this review we will provide an overview on the role of macrophages in the regulation of RBC production, maintenance and clearance. In addition, we will discuss the interactions between these two cell types during transfer of immune complexes and pathogens from RBC to macrophages.

Abstract-It has been hypothesized that an increased hemoglobin level elevates blood pressure. The present study investigated the association between hemoglobin level and systolic blood pressure and diastolic blood pressure in healthy persons. The study population was composed of 101 377 whole blood and plasma donors, who made 691 107 visits to the blood bank. At each visit, hemoglobin level and blood pressure were measured as part of the standard procedure before a blood donation. We used repeated measurement analysis to analyze the data. We used generalized estimating equation models to assess the between-person effect and linear mixed models to assess the within-person effect. All of the analyses were done separately for men and women. In the study population, 50% were men. The mean age in men was 49.3 years (±12.5 years), and in women it was 42.4 years (±13.7 years). Hemoglobin level was positively associated with both systolic and diastolic blood pressures. With respect to the between-person effect, regression coefficients for systolic blood pressure were 1.3 mm Hg per millimole per liter increase in hemoglobin level for men and 1.8 mm Hg per millimole per liter increase in hemoglobin level for women. With respect to the within-person effect, regression coefficients for systolic blood pressure were 0.7 mm Hg and 0.9 mm Hg per millimole per liter increase in hemoglobin level, for men and women, respectively. For diastolic blood pressure, results were comparable. The results show that hemoglobin level is positively associated with both systolic and diastolic blood pressures in healthy individuals. We observed consistent effects between persons but also within persons.

Thrombin and plasmin are the key enzymes involved in coagulation and fibrinolysis. A novel hemostasis assay (NHA) was developed to measure thrombin and plasmin generation in a single well by a fluorimeter. The NHA uses two fluorescent substrates with non-interfering fluorescent excitation and emission spectra. The assay was tested in vitro using modulators like heparin, hirudin, epsilon-aminocaproic acid, gly-pro-arg-pro peptide and reptilase and validated by measurement of prothrombin fragment 1+2 and plasmin-alpha2-antiplasmin levels. Intra- and inter-assay coefficients of variation were < 9% and 6-25%, respectively. Interplay between coagulation and fibrinolysis was demonstrated by the effect of tissue-type plasminogen activator on thrombin generation and by the different responses of activated protein C and thrombomodulin on fibrinolysis. The last responses showed the linkage between coagulation and fibrinolysis by thrombin activatable fibrinolysis inhibitor. In conclusion, this strategy allows detection of coagulation, fibrinolysis and their interplay in a single assay.

BACKGROUND Whole blood donors are at risk of becoming iron deficient. To monitor iron stores, Sanquin implemented a new deferral policy based on ferritin levels, in addition to the traditional hemoglobin measurements. METHODS Ferritin levels are determined in every fifth donation, as well as in all first‐time donors. Donors with ferritin levels <15 ng/mL (WHO threshold) are deferred for 12 months; those ≥15 and ≤30 ng/mL for 6 months. The first results were analyzed and are presented here. RESULTS The results show that 25% of women (N = 20151, 95% CI 24%‐25%) and 1.6% of men (N = 10391, 95% CI 1.4%‐1.8%) have ferritin levels ≤30 ng/mL at their first blood center visit. For repeat (non‐first‐time) donors, these proportions are higher: 53% of women (N = 28329, 95% CI 52%‐54%) and 42% of men (N = 31089, 95% CI 41%‐43%). After a 6‐month deferral, in 88% of returning women (N = 3059, 95% CI 87%‐89%) and 99% of returning men (N = 3736, 95% CI 98%‐99%) ferritin levels were ≥15 ng/mL. After a 12‐month deferral, in 74% of returning women (N = 486, 95% CI 70%‐78%) and 95% of returning men (N = 479, 95% CI 94%‐97%) ferritin levels increased to ≥15 ng/mL. CONCLUSION Deferral of donors whose pre‐donation ferritin levels were ≤30 ng/mL might prevent donors from returning with ferritin levels <15 ng/mL. This policy is promising to mitigate effects of repeated donations on iron stores.

Background and Objectives The aim of this survey was to evaluate the knowledge about Patient Blood Management (PBM) principles and practices amongst clinicians working in seven European hospitals participating in a European Blood Alliance (EBA) project.Materials and Methods A web-based questionnaire was sent to 4952 clinicians working in medical, surgery and anaesthesiology disciplines. The responses were analysed, and the overall results as well as a comparison between hospitals are presented.Results A total of 788 responses (16%) were obtained. About 24% of respondents were not aware of a correlation between preoperative anaemia (POA) and perioperative morbidity and mortality. For 22%, treatment of POA was unlikely to favourably influence morbidity and mortality even before surgery with expected blood loss. More than half of clinicians did not routinely treat POA. 29%, when asked which is the best way to treat deficiency anaemia preoperatively, answered that they did not have sufficient knowledge and 5% chose to 'do nothing'. Amongst those who treated POA, 38% proposed red cell transfusion prior to surgery as treatment. Restrictive haemoglobin triggers for red blood cell transfusion, single unit policy and reduction of number and volumes of blood samples for diagnostic purposes were only marginally implemented.Conclusion Overall, the responses indicated poor knowledge about PBM. Processes to diagnose and treat POA were not generally and homogeneously implemented. This survey should provide further impetus to implement programmes to improve knowledge and practice of PBM.