Source Of Red Blood Cells Research Articles

Using umbilical cord blood as a source of paediatric packed red blood cells: Processing and quality control.

Umbilical cord blood (UCB) has been used as a source of red blood cells (RBCs) for neonatal/paediatric transfusion purposes. This study adopted two different procedures to obtain umbilical RBC (U-RBC) to compare its quality control parameters to those of fractionated adult RBC (A-RBC), for paediatric purposes. UCB units (24) were filtered and processed based on two different methods, namely, conventional/manual (P1;n12) and automatic (P2;n12). They were compared to five fractionated A-RBCs. U-RBC and A-RBC were stored for 14 days and had their haematological, biochemical, haemolytic and microbiological parameters analysed at D1, D7 and D14. Cytokines and growth factors (GFs) in residual U-RBC plasma were measured. Mean volume of processed U-RBC units was 45 mL for P1 and 39 mL for P2; the mean haematocrit level reached 57% for P1 and 59% for P2. A-RBC recorded a mean volume of 44 mL. Haematologic and biochemical parameters analysed in U-RBC and A-RBC presented similar behaviours during storage time, except for parameter values, which differed between them. Pro-inflammatory and immunomodulatory cytokines, as well as GFs, were higher in U-RBC residual plasma than in that A-RBC. UCB can be processed into RBC based on either manual or automated protocols. U-RBC units met the referenced quality parameters defined for A-RBC. Some features, mainly the biochemical ones, should be further investigated to help improve quality parameters, with emphasis on differences found in, and particularities of, this material and on recipients of this new transfusion practice.

Response to ‘The spleen as an unlikely source of red blood cells during increased activity in fishes’

We would like to thank Hedrick and colleagues for their thoughtful comments and for the opportunity to further elaborate on the splenic blood-boosting strategy of Pagothenia borchgrevinki ([Brijs et al., 2020][1]). [Hedrick et al. (2020)][2] argue that the reduction in spleen mass observed in our

A human H1-HBB11-GFP reporter embryonic stem cell line (WAe001-A-2) generated using TALEN-based genome editing.

Hemoglobin production during mammalian development is characterized by temporal switches of the genes coding for the α- and β-globin chains. Defects in this controlled process can lead to hemoglobinapathies such as sickle cell disease and β-thalassemia. The ability of human embryonic stem cells (hESC) to proceed through hematopoiesis could provide a clinically useful source of red blood cells. However, hESC-derived red cells exhibit an embryonic/fetal, but not adult, mode of hemoglobin expression. The resource described here is a hESC line engineered to express a reporter from its adult globin promoter, providing a screening platform for small molecules that lead to efficient induction of adult globin.

Hemagglutination Inhibition Assay.

The hemagglutination inhibition (HI) assay for influenza A virus has been used since the 1940s. The assay may be utilized to detect or quantify antibodies to influenza A viruses and can be used to characterize differences in antigenic reactivity between influenza isolates. In addition, data from HI assays are routinely used for antigenic cartography, influenza virus surveillance, epidemiology, and vaccine-seed strain selection. For antibody quantification, the HI assay is a fast and inexpensive method; other than a source of red blood cells, no expensive or unusual lab equipment is needed, and results can be obtained within a few hours. Historically, the HI assay has also served as a primary method of subtype identification and is still used widely. However, as gene sequencing technology has evolved to be cheaper and faster, it is replacing the HI assay for this purpose.

Blood factory: which stem cells?

Blood transfusions are often essential for treatment of severe anaemia and pregnancy complications. The unavailability of blood is a medical concern, especially in developing countries. New sources of red blood cells (RBC) are under investigation. Several studies have attempted to produce functional RBC from CD34+ haematopoietic stem cells (HSC) isolated from peripheral blood and umbilical cord blood, from embryonic stem cells (ESC) and induced pluripotent stem cells (iPSC). A recent article published in Nature Communications describes a novel model for generating RBC from a stable erythroid cell line obtained from bone marrow CD34+ haematopoietic stem cells (HSC). The cells generated by this method are phenotypically and functionally adult RBC, that resemble very well the donor RBC. In vivo experiments confirmed no difference in the survival of these RBC and donor RBC. The study therefore highlights that this immortalized line is a promising new source of adult RBC.

Auditoría transfusional en un Hospital de Alta Especialidad. Análisis retrospectivo de 12 meses.

Human blood is the only source of red blood cells, platelets and plasma, and includes the clotting factors. Transfusion of concentrated erythrocyte and blood products is a simple form of organ transplant, the benefits of blood transfusion are real, and the life of the patients depends on how is used. to know the transfusion adherence to the recommendations in the Hospital of High Specialty of Veracruz. For a period of 12 months an audit took place in the Transfusion Service of the Hospital of High Specialty of Veracruz, México, on a basis of 3 168 requests for transfusion from which 2314 corresponded to erythrocyte concentrate, 220 to platelet concentrate, 493 to fresh frozen plasma and 41 to cryoprecipitate. An analysis of concordance was made with the different established regulations for a right indication and the results showed that 2171 (67.26%) were appropriate and 1037 were inadequate, which means that the lack of academic training in medicine transfusional affects the risk for patients and cost for Health Institutions.

Immortalisation érythrocytaire pour production de globules rouges in vitro

Population ageing and increase in cancer incidence may lead to a decreased availability of red blood cell units. Thus, finding an alternative source of red blood cells is a highly relevant challenge. The possibility to reproduce in vitro the human erythropoiesis opens a new era, particularly since the improvement in the culture systems allows to produce erythrocytes from induced-Pluripotent Stem Cells (iPSCs), or CD34+ Hematopoietic Stem Cells (HSCs). iPSCs have the advantage of in vitro self-renewal, but lead to poor amplification and maturation defects (high persistence of nucleated erythroid precursors). Erythroid differentiation from HSC allows a far better amplification and adult-like hemoglobin synthesis. But the inability of these progenitors to self-renew in vitro remains a limit in their use as a source of stem cells. A major improvement would consist in immortalizing these erythroid progenitors so that they could expand indefinitively. Inducible transgenesis is the first way to achieve this goal. To date, the best immortalized-cell models involve strong oncogenes induction, such as c-Myc, Bcl-xL, and mostly E6/E7 HPV16 viral oncoproteins. However, the quality of terminal differentiation of erythroid progenitors generated by these oncogenes is not optimal yet and the long-term stability of such systems is unknown. Moreover, viral transgenesis and inducible expression of oncogenes raise important problems in term of safety, since the enucleation rate is not 100% and no nucleated cells having replicative capacities should be present in the final product.

Activation of KLF1 Enhances the Differentiation and Maturation of Red Blood Cells from Human Pluripotent Stem Cells.

Blood transfusion is widely used in the clinic but the source of red blood cells (RBCs) is dependent on donors, procedures are susceptible to transfusion‐transmitted infections and complications can arise from immunological incompatibility. Clinically‐compatible and scalable protocols that allow the production of RBCs from human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) have been described but progress to translation has been hampered by poor maturation and fragility of the resultant cells. Genetic programming using transcription factors has been used to drive lineage determination and differentiation so we used this approach to assess whether exogenous expression of the Erythroid Krüppel‐like factor 1 (EKLF/KLF1) could augment the differentiation and stability of iPSC‐derived RBCs. To activate KLF1 at defined time points during later stages of the differentiation process and to avoid transgene silencing that is commonly observed in differentiating pluripotent stem cells, we targeted a tamoxifen‐inducible KLF1‐ERT2 expression cassette into the AAVS1 locus. Activation of KLF1 at day 10 of the differentiation process when hematopoietic progenitor cells were present, enhanced erythroid commitment and differentiation. Continued culture resulted the appearance of more enucleated cells when KLF1 was activated which is possibly due to their more robust morphology. Globin profiling indicated that these conditions produced embryonic‐like erythroid cells. This study demonstrates the successful use of an inducible genetic programing strategy that could be applied to the production of many other cell lineages from human induced pluripotent stem cells with the integration of programming factors into the AAVS1 locus providing a safer and more reproducible route to the clinic. Stem Cells 2017;35:886–897

Anti-Vel alloimmunization and severe hemolytic disease of the fetus and newborn.

Only rare cases of anti-Vel-associated mild-to-moderate hemolytic disease of the fetus and newborn have been previously reported. No case of fetal anemia requiring prenatal therapy has been noted to date. We report such a case recently encountered at our Fetal Center. Strategies are discussed for managing pregnancy complicated with alloimmunization to an antibody to a high-prevalence antigen, including sources of red blood cells for intrauterine transfusions.

Culturing red blood cells from stem cells: a solution to present and future challenges of transfusion medicine?

Transfusion needs are diversely fulfilled globally. Besides, with population ageing, the various problems faced by healthcare systems will become more and more prominent. As a consequence, the current model of blood supply has to be strengthened, and new sources of red blood cells (RBC) are welcome. A cell therapy approach, in which so‐called ‘cultured RBC’ (cRBC) are generated in vitro, might be a solution. We report here on the various obstacles that were overcome during the past decade to generate cRBC from various sources of stem cells (SC) and also discuss the next developments which will be required to achieve this goal. To date, the culmination point in the field has been the proof of principle of transfusion of cRBC into human, produced from autologous haematopoietic stem and progenitor cells (HSPC), which allowed to demonstrate a favourable life span of cRBC when compared with their native counterpart. The best available source of highly proliferative adult SC is cord blood (CB), which could allow to produce tens of RBC concentrates (RBCC) from one average CB. However, this source is quantitatively limited in number, and more research on HSPC isolated from peripheral blood (PB) is needed. In parallel, critical advances have allowed in vitro production of functional RBC from human pluripotent SC, either embryonic (ESC) or induced (iPS). As iPS can proliferate indefinitely and can be selected for a specific patient phenotype, they appear to be the most favourable SC source, but the protocols still need to be optimized. Most recently, erythroid cell lines have also been envisaged to produce RBC. The major challenges remaining today are economic and technological in order to lead to a cost‐effective process for large‐scale production.

In vitro parameters of cryopreserved leucodepleted and non-leucodepleted red blood cells collected by apheresis or from whole blood and stored in AS-3 for 21 days after thawing.

The aim of the study was to evaluate the in vitro quality of cryopreserved red blood cells obtained from different sources with or without leucodepletion and stored at 4±2 °C in AS-3 for up to 21 days. Red blood cells were collected by four methods: double erythrocytapheresis, whole blood collection with buffy coat removal, double erythrocytapheresis with in-line leucofiltration, or whole blood collection with in-line leucofiltration. All four types of red blood cells were frozen in 40% glycerol after collection and stored at a temperature below -65 °C for at least 30 days, thawed, deglycerolised and subsequently reconstituted in AS-3. The in vitro haematological and biochemical properties of the thawed red blood cells were tested on days 0, 7, 14, and 21 after deglycerolisation and reconstitution. Overall, 72 units were processed. Leucodepletion of cryopreserved red blood cells units reduced haemolysis, lowered ammonia concentration, preserved pH and osmolality and led to sustained higher concentrations of ATP. In contrast, the source of red blood cells (apheresis or whole blood) did not affect their quality. The quality of all investigated red blood cells units was the same as or even better than that of erythrocytes obtained from double erythrocytapheresis with a 24-hour survival of at least 86% after up to 3 weeks of storage in AS-3.

Induced Pluripotent Stem Cells and Erythrocyte Production

Abstract SCI-38Induced pluripotent stem cells (iPSCs) are somatic cells that have been turned into embryonic-like stem cells by forced expression of factors critical for establishing pluripotency. Because iPSCs can be differentiated into any type of cell in the human body, including hematopoietic cells, they are seen as a logical alternative source of red blood cells (RBCs) for transfusion. In addition, the unlimited expansion potential of iPSCs makes it easy to adopt iPSC technology for RBC biomanufacturing. iPSCs can be generated from any type of donor, including O/Rh-negative universal donors and donors with very rare blood phenotypes, which makes it possible to generate blood products to accommodate virtually all patient groups. We have developed an approach for generating large quantities of RBCs from iPSCs by inducing them to differentiate into CD34+CD43+ hematopoietic progenitors in coculture with OP9 stromal cells, followed by selective expansion of erythroid cells in serum-free media with erythropoiesis-supporting cytokines. Erythroid cultures produced by this approach consist of leukocyte-free populations of CD235a+ RBCs with robust expansion potential and long (up to 90 days) life spans. In these cultures, up to 1.8×105 RBCs can be generated from a single iPSC. Similar to embryonic stem cells, iPSC-derived RBCs express predominantly embryonic and fetal hemoglobin, with very little adult hemoglobin. It is already feasible to adopt iPSC technologies for producing cGMP-grade RBCs using defined animal-product-free differentiation conditions. However, the induction of the complete switch from embryonic to fetal and adult hemoglobin, as well as the terminal maturation and enucleation of iPSC-derived erythroid cells, remains a significant challenge. We recently identified at least three distinct waves of hematopoietic progenitors with erythroid potential in iPSC differentiation cultures. The characterization of erythroid cells produced from these waves of hematopoiesis may help to define populations with definitive erythroid potential and facilitate the production of erythrocytes from iPSCs. Additional critical steps toward translating iPSC-based RBC technologies to the clinic include the development of bioreactor-based-technology for further scaling-up of cell production, and evaluation of the therapeutic potential and safety of human pluripotent stem cell-derived blood cells in animal models. Overall, the manufacturing of RBCs provides several advantages. It can improve the continuity of the blood supply, minimize/eliminate the risk of infection transmission, reduce the incidence of hemolytic and nonhemolytic transfusion reactions, and provide an opportunity to generate RBCs that fit specific clinical needs by using genetically engineered iPSCs or iPSCs with rare blood groups. Disclosures:Slukvin:CDI: Consultancy, Equity Ownership; Cynata: Equity Ownership, Membership on an entity's Board of Directors or advisory committees.

RETRACTED: From Stem Cell to Red Blood Cells In Vitro: “The 12 Labors of Hercules”

This article describes the research in progress that will permit the large-scale production of human red blood cells from hematopoietic stem cells. It also discusses the current state of this research, suggests the obstacles to be overcome to pass from the laboratory model to clinical practice, and analyzes the possible indications in the medium and long term. The potential interest of pluripotent stem cells as an unlimited source of red blood cells is considered. If it succeeds, this new approach could mark a considerable advance in the field of transfusion.

Genetically engineered pig red blood cells for clinical transfusion: initial in vitro studies

Pigs are a potential source of red blood cells (RBCs) and could resolve the shortage of human blood for transfusion. This study investigated in vitro the compatibility of genetically engineered pig RBCs (pRBCs) with the human innate immune response. Human volunteers of all ABO blood types were sources of sera and those of O blood type were sources of circulating monocytes/macrophages. RBCs from ABO-compatible (ABO-C) and ABO-incompatible (ABO-I) humans and wild-type (WT) and alpha-1,3-galactosyltransferase gene-knockout (GTKO) pigs were tested for hemagglutination, immunoglobulin (Ig)M/IgG antibody binding, and complement-dependent cytotoxicity (CDC) using human sera. Phagocytosis of RBCs by human monocyte-derived macrophages was measured by coculture in the absence or presence of pooled human O serum. RBCs showed significant differences (p < 0.01) with regard to hemagglutination, IgM and IgG binding, and CDC (ABO-C < GTKO < ABO-I < WT). In the absence of pooled human O serum (antibodies), there was no phagocytosis of any RBCs; in the presence of serum (antibodies), phagocytosis of ABO-I RBCs was greater than of WT (p < 0.01), which in turn was greater than of GTKO RBCs (p < 0.05). GTKO RBCs were significantly more compatible than ABO-I and WT RBCs, but were not comparable to ABO-C combinations. In the presence of antibody, human monocyte-derived macrophages phagocytosed ABO-I RBC/sera combinations more efficiently than pRBCs. These observations contribute to our ultimate goal of using genetically engineered pRBCs for clinical blood transfusion. However, pigs will require other modifications or manipulations if they are to become suitable for human transfusion.

In vitro clinical‐grade generation of red blood cells from human umbilical cord blood CD34+ cells

There is no appropriate alternative source of red blood cells (RBCs) to relieve the worsening shortage of blood available for transfusion. Therefore, in vitro generation of clinically available RBCs from hematopoietic stem cells could be a promising new source to supplement the blood supply. However, there have been few studies about the generation of clinical-grade RBCs by coculture on human mesenchymal stem cells (MSCs) and various cytokine supplements, even though the production of pure RBCs requires coculture on stromal cells and proper cytokine supplements. Umbilical cord blood (CB) CD34+ cells were cultured in serum-free medium supplemented with two cytokine sets of stem cell factor (SCF) plus interleukin-3 (IL-3) plus erythropoietin (EPO) and SCF plus IL-3 plus EPO plus thrombopoietin (TPO) plus Flt-3 for 1 week, followed by coculture upon MSCs derived from bone marrow (BM) or CB for 2 weeks. Almost pure clinical-grade RBCs could be generated by coculturing with CB-MSCs but not BM-MSCs. Expansion fold and enucleation rate were significantly higher in coculture with CB-MSCs than BM-MSCs. Despite a 2.5-fold expansion of erythroblasts in the presence of TPO and Flt-3 for 8 days, the final RBC count was higher without TPO and Flt-3. This study is the first report on generating clinical-grade RBCs by in vitro culture with human MSCs and compared effectiveness of several cytokines for RBC production. This provides a useful basis for future production of clinically available RBCs and a model of erythropoiesis that is analogous to the in vivo system.

Evaluation of nonleukoreduced red blood cell transfusion units collected at delivery from the placenta

The objective of this study was to evaluate the suitability of cord blood (CB) as a source of red blood cells (RBCs) for autologous transfusion. CB was collected in 150-mL storage containers with citrate phosphate dextrose (CPD) as anticoagulant and stored in either saline, adenine, glucose, and mannitol (SAG-M; n = 18) or phosphate, adenine, glucose, guanosine, saline, and mannitol (PAGGS-M; n = 18) for 35 days at 4 degrees C. Hematologic status and hemolysis were studied. The lipopolysaccharide (LPS)-induced production of tumor necrosis factor (TNF)-alpha and transforming growth factor (TGF)-beta1 from CB monocytes was analyzed after incubation with addition of weekly sampled supernatants from the CB RBC units. Five additional units (PAGGS-M) were leukoreduced and thereafter analyzed as indicated above. Hemolysis increased significantly over time, in SAG-M more than in PAGGS-M. During storage in both media, the number of white blood cells (WBCs) decreased, and the LPS-induced production of TNF-alpha and TGF-beta1 decreased and increased, respectively. There were no significant changes in the LPS-induced production of TNF-alpha and TGF-beta1 in the leukoreduced CB RBC units. Hemolysis in CB RBC units increased significantly over time, and PAGGS-M appears to be superior to SAG-M as a preservation solution for CB RBC. The changes in LPS-induced TNF-alpha and TGF-beta1 production over time were probably caused by substances released from apoptotic and/or necrotic WBCs. Further studies are needed to identify both which substances are responsible for the changes in LPS-induced cytokine release and the clinical significance hereof.

Ex Vivo Production of Transfusable Red Blood Cells at Large Scale from Cord Blood CD34+ Cells Using a Coculture System with Human Telomerase Catalytic Subunit (hTERT)-Transfected Human Stromal Cells at Early Phase and with Acitivated Macrophage from Cord Blood CD34+ Cells at Late Phase.

New sources of red blood cells (RBC) would improve the transfusion capacity of blood centers. Several investigators have previously reported that erythroblasts could be obtained from hematopoietic stem cells including those of cord blood (CB) by in vitro culture. However, transfusion of erythroblasts may not be suitable for supplementation of acute blood loss because it should need some time lag until hemoglobin (RBC) boost in circulation due to the fact that transfused erythroblasts once lodged at bone marrow where they undergo maturation into RBCs which are bound to be released into circulation. We have developed a culture system for producing large quantity of enucleated RBCs (e-RBCs) as well as erythroblasts from CB in vitro: one unit e-RBCs (2 x 1012 RBCs) was obtained from one standard CB unit (corresponding to 2 x 106 CD34+ cells) using a coculture system with hTERT-transfected human stromal cells at early phase followed by with activated macrophage in liquid culture (American Society of Hematology 45th Annual Meeting, SanDiego, 2003). In the present study, we first analyzed the function of those manufactured e-RBCs in comparison of that of adult peripheral blood RBCs (PB-RBCs) or that of eryhthroblasts. The hemoglobin (Hb) content of the e-RBCs quantified by photometric determination was almost equivalent to that of adult PBRBC. A Hb A/Hb F ratio of e-RBC analyzed by high-performance liquid chromatography (HbA: HbF = 35: 65) was between those of CB RBCs (10: 90) and adult PB-RBC (99: 1). Oxygen dissociation curves of e-RBCs measured by Hemox-Analyzer was comparable to that of fresh adult PB-RBCs. The erythroblasts showed adhesive property to stromal cells in vitro but e-RBC did not. When we injected e-RBCs into NOD/SCID mice, they were detectable in circulation while erythroblasts were not. In conclusion, the e-RBCs produced by large-scale culturing system from CB CD34+ cells may be useful for acute blood loss.

Investigation of red blood cells from alpha1,3-galactosyltransferase-knockout pigs for human blood transfusion.

Pigs are a potential source of red blood cells (RBCs) for transfusion into humans, but the presence of galactose-alpha1,3-galactose (Gal) epitopes on their surface, against which humans have anti-Gal, has been perceived as a major barrier. alpha1,3-Galactosyltransferase gene-knockout pigs, which do not express Gal epitopes on RBCs (Gal-/-), have recently become available. In vitro, RBCs from Gal-/- pigs were exposed to sera from naïve humans or baboons or from baboons previously sensitized to pig antigens; immunoglobulin binding was measured by flow cytometry, and cytotoxicity, by a hemolytic assay. In vivo, relatively small numbers of Gal-/- RBCs were transfused into two nonsensitized untreated baboons. The survival of pig RBCs was detected by flow cytometry. In vitro, binding of immunoglobulin (Ig) M from naïve human or baboon sera was detected to Gal-/- RBCs but was significantly less than to Gal+/+ RBCs; IgG binding to Gal-/- RBCs was absent or minimal. Sera had minimal cytotoxicity to Gal-/- RBCs compared to Gal+/+ RBCs. Sensitized baboon sera demonstrated much higher IgG binding to Gal-/- RBCs and increased cytotoxicity, but again these were less than to Gal+/+ RBCs. In vivo, the transfusion of relatively small volumes of Gal-/- RBCs was followed by detection of the cells in the baboon's blood for only 5 minutes. Pig RBCs are rapidly phagocytosed from the primate circulation by a mechanism not involving anti-Gal.

PRODUÇÃO DE ENTEROTOXINA TERMOESTÁVEL, HEMOLISINAS, COLICINA E FATORES DE COLONIZAÇÃO EM AMOSTRAS DE Escherichia coli ISOLADAS DE LEITÕES COM DIARRÉIA NO SUDOESTE DO PARANÁ

A E. coli é o principal agente infeccioso envolvido nas diarréias dos leitões. A patogenicidade deste microrganismo é determinada por diversos fatores de virulência, entre os quais destacam-se a presença dos fatores de colonização e toxinas. Nesta pesquisa foram avaliadas 140 cepas de E. coli isoladas de 82 leitões lactentes e 58 recém-desmamados com diarréia em granjas do Sudoeste do Paraná. A detecção da enterotoxina termoestável foi realizada em camundongos neonatos e a colicina verificada em ensaio em ágar com crescimento cruzado em meio semi sólido. Os fatores de colonização foram avaliados através da técnica de microhemaglutinação frente a eritrócitos de diferentes espécies animais. Em 37 (26,4%) e 26 (18,6%) amostras foram verificadas atividade hemolítica e colicinogênica respectivamente. A toxina termoestável foi sintetizada por apenas 17 (12,1%) amostras. A presença de fatores de colonização manose resistente foi observada em 87 (62,1%) amostras analisadas e 41 (29,3%) amostras expressaram fímbria tipo 1.

The hemolytic activity of six arachnid cationic peptides is affected by the phosphatidylcholine-to-sphingomyelin ratio in lipid bilayers

The hemolytic activity of six cationic amphipathic peptides (Oxki1, Oxki2, Pin1, Pin2, IsCT1 and IsCT2) from arachnids strongly depends on the source of red blood cells. The hemolytic activity of the amphipathic peptides was correlated to the phosphocholine-to-sphingomyelin ratio (PC/SM) content, the potency order of which on mammal erythrocytes ranked as follows Guinea pig>pig>sheep. The spider peptides, Oxki1 and Oxki2, prefer small unilamellar vesicles (SUV) composed of PC, but they could not disrupt SUVs made of SM only. Moreover, the membrane-disrupting activity of the scorpion peptide Pin1 was affected by increasing concentrations of SM. Only the scorpion hemolytic peptide Pin2 was able to disrupt SUVs composed merely of SM at high concentrations. Finally, the short scorpion peptides IsCT1 and IsCT2 seem to tolerate high concentrations of SM in the presence of PC for disruption of SUVs; however, the disrupting activities of IsCT1 and IsCT2 are much lower than that of the other four hemolytic peptides. The hemolytic activity caused by all six cationic peptides in mammalian erythrocytes was positively correlated to increases in temperature and increases in the concentration of benzyl alcohol, a membrane fluidizing agent. It was concluded that the hemolytic activity of the cationic peptides strongly depends on the PC/SM content of mammalian erythrocytes, in which cell membranes with a low PC/SM ratio (i.e., of low fluidity) were less disturbed than membranes with a high PC/SM ratio (i.e., of high fluidity).