Selected CD molecules and the phagocytosis of microvesicles released from erythrocytes ex vivo.

BACKGROUND AND OBJECTIVES: The accumulation of microvesicles in erythrocyte concentrates during storage or irradiation may be responsible for clinical symptoms such as inflammation, coagulation and immunization. Our aim was to determine whether any of the cluster of differentiation (CD) molecules responsible for important functions are present on microvesicles, and if their expression level is dependent on the storage period of erythrocyte concentrates. MATERIAL AND METHODS: Erythrocyte microvesicles were isolated from 'fresh' (2nd day) and 'old' (42nd day) stored erythrocyte concentrates. Qualitative cytometric analysis of 0·5 µm, erythrocyte-derived, PS-exposing vesicles was performed using the annexin V-FITC, anti-CD235a-PE antibody and calibrated beads. The microvesicles were also visualized under a confocal microscope. The expression of the molecules CD235a, CD44, CD47, CD55, CD59 and of phosphatidylserine (PS) was compared using flow cytometry. Measurements of microvesicle phagocytosis by human monocytes were carried out using a flow cytometer and a confocal microscope. RESULTS: The analysis of the microvesicles with calibration beads allowed us to identify these structures with a diameter of about 0·5 µm in the 'fresh' and 'old' samples. At day 2, the microvesicles had elevated expression levels of CD47, reduced expression levels of PS, CD55 and CD59. The phagocytosis index was higher for the microvesicles isolated from the 42-day-old erythrocyte concentrates. CONCLUSION: This research may bring us closer to understanding the factors responsible for erythrocyte ageing and to evaluate the quality of stored red blood concentrates intended for transfusion.

Ultrasound-enhanced scintillation proximity assay for rapid diagnostics.

Scintillation proximity assay (SPA) is a type of radioimmunoassay (RIA). We apply ultrasound enhancement to the general SPA. All assay procedures, including the antibody coating and radiolabeled antigen binding are achieved by simply mixing then standing for 5 min in an ultrasound chamber. No additional incubation time is required. To further demonstrate the capability of the UE-SPA, a quantitative measurement of CD55 in various grades of colon tumors was assessed on human tissue slides. The results showed a significant correlation between CD55 expression and tumorigenesis. In conclusion, we confirmed that UE-SPA is a reliable, rapid and alternative to RIA.

Diminished presentation of complement regulatory protein CD55 on red blood cells from patients with hereditary haemolytic anaemias.

INTRODUCTION: Hereditary haemolytic anaemias (HHA) encompass a heterogeneous group of anaemias characterized by decreased red blood cell survival. The aim of this study was to evaluate the status of red blood cell (RBC) surface molecules known or previously proposed to participate in preventing premature RBC clearance, analysing erythrocytes from patients with two types of HHA: hereditary spherocytosis (HS) and microcytosis. MATERIAL/METHODS: Relative binding of five monoclonal antibodies (mAbs), anti-CD55, anti-CD59, anti-CD44, anti-CD47 and anti-CD58, was evaluated in erythrocytes of patients with HS and hereditary microcytosis, using flow cytometry. The amount of CD55 protein was assessed by semi-quantitative Western blots densitometry analysis. RESULTS: The majority of both HS and microcytic patients demonstrated significant reduction of anti-CD55 binding by erythrocytes (average 23% and 19%, respectively, P < .001), with no concomitant anti-CD59-binding deficiency. Anti-CD44, anti-CD47 and anti-CD58 binding was within the healthy control range or was slightly decreased. CONCLUSIONS: This study provides evidence supporting the presence of erythrocytes deficient in CD55 presentation in HS and hereditary microcytosis. Moreover, deficiency of CD55 antigen presentation on RBC does not correlate with the amount of CD55 in RBC membrane. Further studies using molecular techniques will clarify the exact participation of CD55 deficiency in premature RBC clearance in HHA.

Overexpression of CD55 from Barrett's esophagus is associated with esophageal adenocarcinoma risk.

BACKGROUND AND AIM: Although several molecular biomarkers for esophageal adenocarcinoma (EAC) have been shown to be useful disease indicators, none has been established as a reliable indicator for risk of EAC or have progressed to routine use. The aim was to identify biomarkers of high risk for EAC in patients with Barrett's esophagus (BE). METHODS: Following endoscopic observation by magnified endoscopy with narrow band imaging (ME-NBI), brushing was followed by obtaining biopsy samples from columnar-lined esophagus (CLE) and from EAC lesions of EAC patients, and from age- and sex-matched non-EAC controls with BE. Total RNA was extracted for microarray analysis using Affymetrix GeneChip Human Genome U133 plus 2.0 Array. Real-time-PCR analysis of identified candidate genes was used to confirm the results. RESULTS: Overall, 9 EAC patients and 50 patients with BE were studied. Seventy-nine candidate genes were identified by microarray analysis based on a proportional hazards model (P < 0.005). Six genes exhibited significantly differential expressions in both BE and cancer lesions of the EAC group compared to BE of the controls. In the brushing samples, median CD55 relative expression levels in cancer lesions were highest and decreased in BE of EAC group and BE of the controls, in that order (P < 0.001). CONCLUSION: Over expression of CD55 in brushing samples taken from BE may be associated with the risk of EAC.

Immunohistochemical Expression and Prognostic Significance of CD97 and its Ligand DAF in Human Cervical Squamous Cell Carcinoma.

Accumulating evidences had demonstrated that the CD97, a member of the epidermal growth factor 7-transmembrane family, and its cellular ligand decay accelerating factor (DAF) both play important roles in tumor dedifferentiation, migration, invasiveness, and metastasis. However, the roles of CD97 and DAF in human cervical squamous cell carcinoma (CSCC) have not been investigated. The purpose of this study was to observe the expression profile of CD97 and DAF in CSCC and evaluate their clinical significance. Immunohistochemistry was used to investigate the expression of CD97 and DAF proteins in 97 patients with CSCC and 53 patients with cervical intraepithelial neoplasia, a precursor lesion of CSCC. CD97 and DAF were absent or only weakly expressed in the normal epithelium of the cervix but were present in 83.5% (81/97) and 90.7% (88/97) of CSCC samples, respectively. Overexpression of CD97 was significantly associated with a high International Federation of Gynecology and Obstetrics stage (P=0.010) and lymph node metastasis (P=0.026). The majority of CSCCs, irrespective of staging/grading classification, displayed strong DAF immunostaining. Kaplan-Meier survival analysis revealed that overexpression of CD97 was associated with a worse prognosis. Multivariate analyses showed that the International Federation of Gynecology and Obstetrics stage (P=0.000), lymph node metastasis (P=0.004), and CD97 expression (P=0.040) were independent risk factors for overall survival. The present study suggested that the expressions of CD97 and DAF were both upregulated in CSCC. The expression level of CD97 in CSCC was associated with the severity of the tumor. Furthermore, CD97 might be an independent poor prognostic factor for CSCC patients.

Mesenchymal stem cells engineered to inhibit complement-mediated damage.

Mesenchymal stem cells (MSC) preferentially migrate to damaged tissues and, due to their immunomodulatory and trophic properties, contribute to tissue repair. Although MSC express molecules, such as membrane cofactor protein (CD46), complement decay-accelerating factor (CD55), and protectin (CD59), which confer protection from complement-mediated lysis, MSC are recruited and activated by anaphylatoxins after transplantation, potentially causing MSC death and limiting therapeutic benefit. We have previously demonstrated that transduction of MSC with a retrovirus encoding HCMV-US proteins resulted in higher levels of MSC engraftment due to decreased HLA-I expression. Here, we investigate whether engineering MSC to express US2 (MSC-US2), US3 (MSC-US3), US6 (MSC-US6), or US11 (MSC-US11) HCMV proteins can alter complement recognition, thereby better protecting MSC from complement attack and lysis. HCMV-US proteins increased MSC CD59 expression at different levels as determined by flow cytometric evaluation of the median fluorescence intensity ratio (MFI). A significant increase in CD59 expression was seen in MSC-US2, MSC-US3, and MSC-US6, but not in MSC-US11. Only MSC-US2 displayed increased expression of CD46, while US2 and US3 proteins were both able to augment the percentage of MSC expressing this molecule. Regardless of the HCMV protein expressed, none changed CD55 MFI; however, expression of US6, US11, and US2 each increased the percentage of MSC that were positive for this molecule. Because US2 protein was the most efficient in up-regulating all three complement regulatory proteins, we used a functional complement-mediated cytotoxicity assay to investigate whether MSC-US2 were protected from complement-mediated lysis. We demonstrated that over-expression of the US2 protein reduced complement lysis by 59.10±12.89% when compared to untransduced MSC. This is the first report, to our knowledge, describing a role of HCMV-US proteins in complement evasion, and our data shows that over-expression of US2 protein on MSC could serve as a strategy to protect these cells from complement lysis.

Detection of paroxysmal nocturnal hemoglobinuria-phenotype in patients with chronic lymphocytic leukemia and multiple myeloma.

BACKGROUND: Paroxysmal nocturnal hemoglobinuria (PNH) results due to decrease or absence of glycosylphosphatidylinositol-anchored (GPI) molecules, such as CD55 and CD59, from the surface of the affected cells. PNH-phenotype has been described in various hematological disorders, mainly aplastic anemia and myelodysplastic syndromes; recently it has been reported in patients with lymphoproliferative syndromes and multiple myeloma (MM). MATERIALS AND METHODS: We evaluated the presence of CD55 negative and/or CD59 negative red blood cell (RBC) populations in newly diagnosed treatment naive-54 chronic lymphocytic leukemia (CLL) and 29 MM patients by flow cytometry. RESULTS: PNH-phenotype was not reported in any patient; however, RBC populations deficient in CD55 were detected in 16.66% (9/54) CLL and 6.89% (2/29) MM patients. Clinical presentation or the hematological parameters did not show any relationship with the presence of CD55 deficient RBC population. CONCLUSION: Our study showed absence of PNH-phenotype in patients with CLL and MM; however, isolated CD55 deficient RBC were identified in both CLL and MM. Larger prospective studies by other centers, including simultaneous analysis of granulocytes for the presence of PNH-phenotype, are needed to corroborate these findings and to work out the mechanisms and the significance of the existence of this phenotype in these patients.

[Biological characteristics of CD55(hig); side population in breast cancer cell line MCF-7].

AIM: To determine whether the CD55(hig); expression (CD55(hig);) cells in side population (SP) of the cell line MCF-7 possess characteristics of cancer stem cells. METHODS: Breast cancer cell line MCF-7 was cultured and the nucleic acid dye Hoechst33342 and Verapami were added. Flow cytometry (FCM) was employed to isolate the cells of SP and mian population (MP), the cells were then labeled with CD55 mAb; mean values of fluorescence intensity of CD55 in SP and MP cells were measured. CD55 mAb was used to mark the unsorted MCF-7 cells, the proportion of CD55(hig); cells was determined, and then CD55(hig); cells were sorted and collected, to observe biological characteristics, such as cell morphology, adherence rate, colony formation and cell cycle distribution as well as nude mice implantation. RESULTS: Mean value of fluorescence intensity of CD55 in SP cells was 100.85±4.57, and mean value of fluorescence intensity of CD55 in MP cells was 50.51±4.75; the proportion of CD55(hig); cell in MCF-7 cells was 2.12%; adherent rate of CD55(hig); cells in 24 h was lower than that in CD55(low); cells and 24 h after inoculation adherent rates of both cells had no significant difference (P>0.05); CD55(hig); cells were mostly spherical and kept in a suspended state at 12 hours after inoculation and culture; CD55(hig); cells had the ability of colony formation, the clone-forming rate of CD55(hig); cells was (20.04±1.07)% when the cells were cultured for one week, it was lower than the rate of (27.14±1.07)% in CD55(low); cells (P<0.01); the ratio of G0/G1 resting cells in CD55(hig); cells was (85.4±3.37)% which was higher than that in CD55(low); cells (58.6±2.55)% and in MCF-7 cells (70.73±4.21)%, which had a statistically significant difference (P<0.05). All nude mice implanted with CD55(hig); cells developed the tumor, and the pathological examination of the transplanted tumor had the properties of malignant cells. CONCLUSION: A few CD55(hig); cells were found in breast cancer MCF-7 cells, and most of CD55(hig); cells were quiescent, non-adherent as well as being in a suspended state and being hereditary after cloning, so CD55(hig); cells had biological characteristics of cancer stem cells.

Immunohistochemical localization of complement regulatory proteins in the human retina.

Age-related macular degeneration (AMD) is a complex disease. Genetic studies have found strong associations between AMD and variants of several complement pathway-associated genes. The regulation of the complement cascade seems to be critical in the pathogenesis of AMD. In 45 human donor eyes immunohistochemistry was performed using antibodies directed against major regulators of the complement system: complement factor H (CFH), decay accelerating factor (DAF/CD55), complement receptor 1 (CR1/CD35), and membrane cofactor protein (MCP/CD46). All eyes were classified in AMD and controls. 11 eyes were graded as early AMD. 34 eyes were controls. In all eyes staining was found in intercapillary pillars of choroid adjacent to Bruch's membrane for CFH, at the basal surface of RPE cells for MCP, and at the apical side of the retinal pigment epithelium for CR1. DAF immunoreactivity was increased along the inner segments of rod and cone photoreceptor cells at the level of the external limiting membrane Labeling of soft drusen was found for CFH and CR1. In addition, DAF and CR1 showed staining of ganglion cells in all eyes. CFH and particularly MCP showed decreased or absent staining in eyes with early AMD adjacent to Bruch's membrane. The overlapping expression of regulators at the level of Bruch's membrane and the retinal pigment epithelium shows the importance of this site for control of the complement system. Decreased and therefore unbalanced expression of regulators, as shown in this study for CFH and MCP, may ultimately lead to AMD.

High recovery FASP applied to the proteomic analysis of microdissected formalin fixed paraffin embedded cancer tissues retrieves known colon cancer markers.

Proteomic analysis of samples isolated by laser capture microdissection from clinical specimens requires sample preparation and fractionation methods suitable for small amounts of protein. Here we describe a streamlined filter-aided sample preparation (FASP) workflow that allows efficient analysis of lysates from low numbers of cells. Addition of carrier substances such as polyethylene glycol or dextran to the processed samples improves the peptide yields in the low to submicrogram range. In a single LC-MS/MS run, analyses of 500, 1000, and 3000 cells allowed identification of 905, 1536, and 2055 proteins, respectively. Incorporation of an additional SAX fractionation step at somewhat higher amounts enabled the analysis of formalin fixed and paraffin embedded human tissues prepared by LCM to a depth of 3600-4400 proteins per single experiment. We applied this workflow to compare archival neoplastic and matched normal colonic mucosa cancer specimens for three patients. Label-free quantification of more than 6000 proteins verified this technology through the differential expression of 30 known colon cancer markers. These included Carcino-Embryonic Antigen (CEA), the most widely used colon cancer marker, complement decay accelerating factor (DAF, CD55) and Metastasis-associated in colon cancer protein 1 (MACC1). Concordant with literature knowledge, mucin 1 was overexpressed and mucin 2 underexpressed in all three patients. These results show that FASP is suitable for the low level analysis of microdissected tissue and that it has the potential for exploration of clinical samples for biomarker and drug target discovery.

Flow cytometric analysis of erythrocytes in paroxysmal nocturnal hemoglobinuria reveals superiority of CD59 as a diagnostic marker compared to CD55.

CONTEXT: Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal stem cell disorder characterized by complement-mediated hemolysis due to reduced expression of glycosyl phosphatidylinositol-anchored complement deactivating proteins such as CD55 and CD59 on RBC. Flow cytometric analysis of CD55 and CD59 expression by RBC is a reliable tool for the diagnosis of PNH. AIMS: Detection and quantification of PNH clone and comparison of the relative role of CD55 and CD59 expression by RBC in the diagnosis of PNH. MATERIALS AND METHODS: Flow cytometric analysis of RBC was performed in blood samples of 239 patients by direct immunofluorescence using monoclonal anti-CD55 and anti-CD59 antibodies. CD55 and CD59 expressions by RBC were compared in 54 cases in which PNH clones were detected. RESULTS: Out of 54 cases, 85% and 72% revealed CD59 and CD55 negative populations, respectively. Various combinations of type II and III erythrocytes could be identified in all cases having CD59 deficient RBC. In contrast, distinct populations of CD55-deficient RBC were seen in only 33% cases. In the remaining (67%) cases, CD55 negative RBC caused sloping of the ascending limb of the histogram resulting in difficulties in interpretation. Fifteen percent cases had false CD55-deficient RBC and in 23% cases anti-CD55 antibody failed to identify PNH clones which were detected by CD59. CONCLUSION: CD59 is a better marker for the diagnosis of PNH. Although CD55 negativity supported the diagnosis of PNH in cases with CD59-deficient RBC, its role as an independent diagnostic marker for PNH is questionable due to its lower sensitivity and specificity.

Multiparameter flow cytometry for the diagnosis and monitoring of small GPI-deficient cellular populations.

BACKGROUND: Glycosyl-phosphatidylinositol (GPI)-negative blood cells are diagnostic for Paroxysmal Nocturnal Hemoglobinuria (PNH). Marrow failure states are often associated with GPI-negative cell populations. Quantification of small clonal populations of GPI-negative cells influences clinical decisions to administer immunosuppressive therapy in marrow failure states (aplastic anemia or myelodysplastic syndrome) and to monitor minimal residual disease after allogeneic blood or marrow transplantation (BMT). We studied the reliability of high-resolution flow cytometry markers operating at the limits of detection. METHODS: We performed serial quantification of the PNH clone size in 38 samples using multiparameter flow cytometry. Granulocytes, monocytes, and RBCs were gated using forward and side scatter as well as lineage-specific markers. The GPI-linked markers fluorescent aerolysin (FLAER), CD55, and CD59 were comparatively evaluated. We also evaluated CD16 on granulocytes and CD14 on monocytes. The sensitivity of detection by each marker was further defined by serial dilution experiments on a flow-sorted sample. Two patients had quantification of their GPI-negative clones before and after allogeneic BMT. RESULTS: FLAER was the most discriminant marker and allowed identification of 0.1% of GPI-negative cells despite other markers having superior signal-to-noise characteristics. CD14 and CD16 were inferior to CD55 at lower concentrations and in clinical application. CONCLUSIONS: Multiparameter flow cytometry permits quantification of small GPI-negative clones with a sensitivity limit of about 0.1%. The single most reliable marker to monitor small granulocyte or monocyte PNH clones is FLAER, especially in conditions such as myelodysplastic syndromes or BMT, when traditional GPI-linked surface marker expression can be significantly altered. © 2010 International Clinical Cytometry Society.

Paroxysmal nocturnal haemoglobinuria: diagnostic tests, advantages, & limitations.

Paroxysmal nocturnal haemoglobinuria (PNH) is a rare acquired clonal disorder of haematopoietic stem cells. The molecular defect in PNH is mutation in the phosphotidylinositol glycan complementation class A (PIGA gene) causing defect in glycosylphosphatidylinositol anchored proteins (Cell, 73, 1993, 703). The deficiency of these GPI-anchored proteins on the membranes of haematopoietic cells lead to the various clinical manifestations of PNH. Clinically PNH is classified into classic PNH, PNH in the setting of another specified bone marrow disorder and sub clinical PNH. Size of the PNH clone differs in these different subtypes. The management of PNH has been revolutionized by the advent of monoclonal antibody, eculizumab. Thus, today it is important to have sensitive tests to diagnose and monitor the clone size in patients of PNH. Before 1990, diagnosis of PNH was made using complement based tests. However in the last decade, flowcytometry has become the gold standard diagnostic test as it has increased sensitivity to detect small clones, ability to measure clone size and is not affected by blood transfusions. This review is aimed to focus mainly on the different methods available for the detection of PNH clone and the recent advances and recommendations for the flowcytometric diagnosis of PNH.

Current status of allogeneic hematopoietic stem cell transplantation for paroxysmal nocturnal hemoglobinuria.

Treatment of patients with paroxysmal nocturnal hemoglobinuria (PNH) has been traditionally empirical, primarily aiming at ameliorating symptoms or treating complications resulting from the disease. Novel therapies such as eculizumab result in stabilization of hemoglobin levels and improvement in quality of life, but does not cure PNH. Nonrandomized studies suggest that long-term remissions are achievable when using myeloablative or nonmyeloablative/reduced-intensity (NMT/RIC) allogeneic hematopoietic stem cell transplantation (HSCT) as treatment for PNH. Nevertheless, patients with previous life-threatening complications from PNH may be more appropriately treated with an NMT/RIC regimen, rather than a myeloablative approach, because of the increased transplant mortality associated with the latter. The decision to perform an allogeneic HSCT (allo-HSCT) should weigh disease prognosis, by incorporating known adverse prognostic factors such as previous history of thrombosis and/or evolution to pancytopenia, among others, against the risk of transplant-related complications. Selection of the appropriate candidate and, equally important, the right time to perform an allo-HCT are important questions that need to be answered in the context of large prospective randomized trials.

Hypoxia increases susceptibility of non-small cell lung cancer cells to complement attack.

The complement system can be specifically targeted to tumor cells due to molecular changes on their surfaces that are recognized by complement directly or via naturally occurring antibodies. However, tumor cells often overexpress membrane-bound complement inhibitors protecting them from complement attack. We have previously shown that non-small cell lung cancer (NSCLC) cells, additionally to membrane-bound inhibitors, produce substantial amounts of soluble regulators such as factor I (FI) and factor H (FH). Since low oxygen concentration is associated with rapidly growing solid tumors, we studied how NSCLC cells protect themselves from complement attack under hypoxic conditions. Unexpectedly, mRNA levels and secretion of both FI and FH were significantly decreased already after 24 h exposure to hypoxia while cell viability measured by XTT assay and annexin V/7-AAD staining was affected only marginally. Furthermore, we observed decrease of mRNA level and loss of membrane-bound complement inhibitor CD46 and increased deposition of early (C3b) and terminal (C9) complement components on hypoxic NSCLC cells. All three complement pathways (classical, lectin and alternative) were employed to deposit C3b on cell surface. Taken together, our results imply that under hypoxic conditions NSCLC give up some of their available defense mechanisms and become more prone to complement attack.

PNH revisited: Clinical profile, laboratory diagnosis and follow-up.

BACKGROUND: Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by intravascular hemolysis, marrow failure, nocturnal hemoglobinuria and thrombophila. This acquired disease caused by a deficiency of glycosylphosphatidylinositol (GPI) anchored proteins on the hematopoietic cells is uncommon in the Indian population. MATERIALS AND METHODS: Data of patients diagnosed with PNH in the past 1 year were collected. Clinical data (age, gender, various presenting symptoms), treatment information and follow-up data were collected from medical records. Results of relevant diagnostic tests were documented i.e., urine analysis, Ham's test, sucrose lysis test and sephacryl gel card test (GCT) for CD55 and CD59. RESULTS: A total of 5 patients were diagnosed with PNH in the past 1 year. Presenting symptoms were hemolytic anemia (n=4) and bone marrow failure (n=1). A GCT detected CD59 deficiency in all erythrocytes in 4 patients and CD55 deficiency in 2 patients. A weak positive PNH test for CD59 was seen in 1 patient and a weak positive PNH test for CD55 was seen in 3 patients. All patients were negative by sucrose lysis test. Ham's test was positive in two cases. Patients were treated with prednisolone and/or androgen and 1 patient with aplastic anemia was also given antithymocyte globulin. A total of 4 patients responded with a partial recovery of hematopoiesis and 1 patient showed no recovery. None of the patients received a bone marrow transplant. CONCLUSION: The study highlights the diagnostic methods and treatment protocols undertaken to evaluate the PNH clone in a developing country where advanced methods like flowcytometry immunophenotyping (FCMI) and bone marrow transplants are not routinely available.

Paroxysmal nocturnal hemoglobinuria may cause retinal vascular occlusions.

BACKGROUND: Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by the classic triad of haemolytic anaemia, thrombophilia and cytopenia with the majority of cases occurring in adulthood. PNH constitutes a nonmalignant clonal disease of hematopoietic stem cells harboring somatic mutations in the X-linked phosphatidyl inositol glycan complementation group-A (PIG-A) gene. METHODS: We report for the first time retinal venous vascular occlusion as the primary manifestation of PNH. A patient of untypical age for retinal vascular occlusions presented with a history of 4 weeks of progressive reduction in visual acuity. RESULTS: The screening tests for thrombophilia were not successful. However, elevated LDH was detected, leading to the diagnosis of PNH. CONCLUSIONS: To date, no report shows retinal vascular occlusion as the primary symptom leading to the diagnosis PNH. This article describes, for the first time, that this rare disease needs to be considered in the differential diagnosis of retinal vascular occlusions.

Increased deposition of C3b on red cells with low CR1 and CD55 in a malaria-endemic region of western Kenya: implications for the development of severe anemia.

BACKGROUND: Severe anemia due to Plasmodium falciparum malaria is a major cause of mortality among young children in western Kenya. The factors that lead to the age-specific incidence of this anemia are unknown. Previous studies have shown an age-related expression of red cell complement regulatory proteins, which protect erythrocytes from autologous complement attack and destruction. Our primary objective was to determine whether in a malaria-endemic area red cells with low levels of complement regulatory proteins are at increased risk for complement (C3b) deposition in vivo. Secondarily, we studied the relationship between red cell complement regulatory protein levels and hemoglobin levels. METHODS: Three hundred and forty-two life-long residents of a malaria-holoendemic region of western Kenya were enrolled in a cross-sectional study and stratified by age. We measured red cell C3b, CR1, CD55, and immune complex binding capacity by flow cytometry. Individuals who were positive for malaria were treated and blood was collected when they were free of parasitemia. Analysis of variance was used to identify independent variables associated with the %C3b-positive red cells and the hemoglobin level. RESULTS: Individuals between the ages of 6 and 36 months had the lowest red cell CR1, highest %C3b-positive red cells, and highest parasite density. Malaria prevalence also reached its peak within this age group. Among children 6 to

Detection of CD55- and CD59-deficient granulocytic populations in patients with myelodysplastic syndrome.

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by absence of CD55 and CD59 from the surface of affected cells. PNH has been associated with myelodysplastic syndromes (MDS). The aim of our study was to estimate the prevalence of the PNH clone in MDS patients by detecting CD55 and CD59 deficiency. We studied 90 MDS patients: 19 patients with RA, 15 with refractory anemia with ringed sideroblasts (RARS), 18 with refractory anemia with excess of blasts (RAEB), 17 with refractory anemia with excess of blasts in transformation (RAEB-t), and 21 with chronic myelomonocytic leukemia (CMML). Twenty healthy individuals were also studied as the control group. We studied the PNH clone on granulocytes of these patients with the aid of flow cytometry. CD55- and CD59-deficient granulocytic populations were detected in 15.5% of MDS patients compared to 2.8% of normal individuals. Among the subgroups of the study, significant difference was present in three cases: (1) between CMML and control, (2) between CMML and RA, and (3) between CMML and RARS. These data indicate a possible association between PNH phenotype and MDS. MDS patients of worse prognosis (CMML) express more strongly the PNH clone compared to those of better prognosis (RA and RARS). Perhaps, the examination of MDS patients for the PNH clone by flow cytometry could provide us with a valuable prognostic tool.

Complement activation in Ghanaian children with severe Plasmodium falciparum malaria.

BACKGROUND: Severe anaemia (SA), intravascular haemolysis (IVH) and respiratory distress (RD) are severe forms of Plasmodium falciparum malaria, with RD reported to be of prognostic importance in African children with malarial anaemia. Complement factors have been implicated in the mechanism leading to excess anaemia in acute P. falciparum infection. METHODS: The direct Coombs test (DCT) and flow cytometry were used to investigate the mean levels of RBC-bound complement fragments (C3d and C3balphabeta) and the regulatory proteins [complement receptor 1 (CD35) and decay accelerating factor (CD55)] in children with discrete clinical forms of P. falciparum malaria. The relationship between the findings and clinical parameters including coma, haemoglobin (Hb) levels and RD were investigated. RESULTS: Of the 484 samples tested, 131(27%) were positive in DCT, out of which 115/131 (87.8%) were positive for C3d alone while 16/131 (12.2%) were positive for either IgG alone or both. 67.4% of the study population were below 5 years of age and DCT positivity was more common in this age group relative to children who were 5 years or older (Odds ratio, OR = 3.8; 95%CI, 2.2-6.7, p < 0.001). DCT correlated significantly with RD (beta = -304, p = 0.006), but multiple regression analysis revealed that, Hb (beta = -0.341, p = 0.012) and coma (beta = -0.256, p = 0.034) were stronger predictors of RD than DCT (beta = 0.228, p = 0.061). DCT was also not associated with IVH, p = 0.19, while spleen size was inversely correlated with Hb (r = -402, p = 0.001). Flow cytometry showed similar mean fluorescent intensity (MFI) values of CD35, CD55 and C3balphabeta levels on the surfaces of RBC in patients and asymptomatic controls (AC). However, binding of C3balphabeta correlated significantly with CD35 or CD55 (p < 0.001). CONCLUSION: These results suggest that complement activation contributed to anaemia in acute childhood P. falciparum malaria, possibly through induction of erythrophagocytosis and haemolysis. In contrast to other studies, this study did not find association between levels of the complement regulatory proteins, CD35 and CD55 and malarial anaemia. These findings suggest that complement activation could also be involved in the pathogenesis of RD but larger studies are needed to confirm this finding.