Application of lyophilised human platelets for antibody detection in solid phase red cell adherence assay.

Antibodies against human platelets cause a variety of thrombocytopenic disorders, which lead to potentially fatal haemorrhage. Therefore, their prompt detection is mandatory for successful patient treatment. Solid phase red cell adherence (SPRCA) assay allows for platelet antibody detection widely. However, preparation of fresh platelets with HLA-I and human platelet antigens (HPA)1-5,15 genotyped as target cells is inconvenient and fresh platelets have a short shelf life. In this study, the lyophilised human platelets for antibody detection in SPRCA were prepared. Firstly, platelets were resuspended in lyophilisation buffer and freeze-dried. Then the characteristics of lyophilised platelet were analysed. Rehydrated platelets were recovered with a mean rate of 80.91% ± 2.87%, and still retained spherical morphology. Indirect flow cytometry showed that glycoproteins IIb/IIIa, Ia/IIa, Ib/IX, IV, CD109, and HLA class I were present on the surface of the lyophilised platelets at a comparable level to that of fresh platelets. The consistent results obtained with WHO reference reagents containing anti-HPA-1a, anti-HPA-3a, and anti-HPA-5b, as well as clinical samples from the same donors containing anti-HLA antibodies when reacting with lyophilised versus fresh platelets confirmed good antigenicity preservation of platelets after freeze-drying. Further investigation showed that the lyophilised platelets could be stored at 2-8 °C for up to 14 months and the reconstituted suspension was stable for 48 h. Therefore, lyophilised platelets can be a convenient alternative to fresh platelets to use for anti-platelet antibody detection in SPRCA tests.

RORA Overexpression Alleviates Nasal Mucosal Injury and Enhances Red Blood Cell Immune Adhesion Function in a Mouse Model of Allergic Rhinitis via Inactivation of the Wnt/ß-Catenin Signaling Pathway.

BACKGROUND: In this study, we examined whether RORA (retinoic acid receptor-related orphan receptor alpha) was capable of alleviating the progression of allergic rhinitis (AR). METHODS: In order to elucidate the possible effects of RORA and the regulatory mechanism between RORA and the Wnt/ß-catenin signaling pathway, mouse AR models were established and treated with RORA vector, siRNA against RORA, or the Wnt/ß-catenin pathway inhibitor WIF-1. Subsequently, the serum levels of inflammatory cytokines (IgE, INF-γ, IL-1ß, IL-4, and IL-17), red blood cell (RBC) immune adhesion function, the levels of RORA, ß-catenin, and GSK3ß, as well as the extent of ß-catenin and GSK-3ß phosphorylation were evaluated and measured. RESULTS: The OVA-induced AR mouse model exhibited obvious nasal mucosal injury and inflammatory cell infiltration. RORA overexpression or the inactivation of the Wnt/ß-catenin signaling pathway was uncovered as a way to ameliorate nasal mucosal injury and eosinophil infiltration of the OVA-induced AR mouse model. On the other hand, it reduced the number of eosinophils and mast cells, which also resulted in downregulated expression of IgE, INF-γ, IL-1ß, IL-4, IL-17, ß-catenin, and GSK-3ß. Moreover, this led to a decreased extent of ß-catenin and GSK-3ß phosphorylation, while the rates of C3b receptor rosette and Ic rosette were elevated. CONCLUSION: Taken together, the key findings provided evidence suggesting that the elevated RORA could potentially alleviate nasal mucosal injury and simultaneously enhance RBC immune adhesion function through the inhibition of the Wnt/ß-catenin signaling pathway activation in an OVA-induced AR mouse model. This emphasizes a novel therapeutic target for the treatment of AR.

Type IV Pili Promote Clostridium difficile Adherence and Persistence in a Mouse Model of Infection.

Cyclic diguanylate (c-di-GMP) is a second messenger that regulates the transition from motile to sessile lifestyles in numerous bacteria and controls virulence factor production in a variety of pathogens. In Clostridium difficile, c-di-GMP negatively regulates flagellum biosynthesis and swimming motility and promotes the production of type IV pili (TFP), biofilm formation, and surface motility in vitro Flagella have been identified as colonization factors in C. difficile, but the role of TFP in adherence to host cells and in colonization of the mammalian gut is unknown. Here we show that c-di-GMP promotes adherence to epithelial cells in vitro, which can be partly attributed to the loss of flagella. Using TFP-null mutants, we demonstrate that adherence to epithelial cells is partially mediated by TFP and that this TFP-mediated adherence requires c-di-GMP regulation. In a mouse model of colonization, the TFP-null mutants initially colonized the intestine as well as the parental strain but were cleared more quickly. Moreover, compared to the parent strain, C. difficile strains lacking TFP were particularly deficient in association with the cecal mucosa. Together these data indicate that TFP and their positive regulation by c-di-GMP promote attachment of C. difficile to the intestinal epithelium and contribute to persistence of C. difficile in the host intestine.

Development of Immunoassays for Burkholderia pseudomallei Typical and Atypical Lipopolysaccharide Strain Typing.

Burkholderia pseudomallei is the causative agent of melioidosis, a severe infection endemic to many tropical regions. Lipopolysaccharide (LPS) is recognized as an important virulence factor used by B. pseudomallei Isolates of B. pseudomallei have been shown to express one of four different types of LPS (typical LPS, atypical LPS types B and B2, and rough LPS) and in vitro studies have demonstrated that LPS types may impact disease severity. The association between LPS types and clinical manifestations, however, is still unknown, in part because an effective method for LPS type identification is not available. Thus, we developed antigen capture immunoassays capable of distinguishing between the LPS types. Mice were injected with B or B2 LPS for atypical LPS-specific monoclonal antibody (mAb) isolation; only two mAbs (3A2 and 5B4) were isolated from mice immunized with B2 LPS. Immunoblot analysis and surface plasmon resonance demonstrated that 3A2 and 5B4 are reactive with both B2 and B LPS where 3A2 was shown to possess higher affinity. Assays were then developed using capsular polysaccharide-specific mAb 4C4 for bacterial capture and 4C7 (previously shown to bind typical LPS) or 3A2 mAbs for typical or atypical LPS strain detection, respectively. The evaluations performed with 197 strains of Burkholderia and non-Burkholderia species showed that the assays are reactive to B. pseudomallei and Burkholderia mallei strains and have an accuracy of 98.8% (zero false positives and two false negatives) for LPS typing. The results suggest that the assays are effective and applicable for B. pseudomallei LPS typing.

Importance of Quality of Life for Adherence to Sublingual Immunotherapy.

Background. Nonperception of efficacy ranks among the most commonly cited causes for nonadherence to sublingual immunotherapy (SLIT). Quality of life (QoL) in patients is a determining factor influencing adherence. We investigated QoL and adherence separately in SLIT patients at one pediatric practice in Germany. Methods. We conducted a noninterventional, cross-sectional, retrospective, quality-of-life survey among pediatric patients treated with SLIT. QoL was assessed using the generic SF-12 health survey in German. The items contained in the SF-12 health survey are weighted, added up, and converted to obtain a physical component score (PCS) and a mental component score (MCS). Each component score ranges from 0 to 100; the higher the score, the better the QoL perceived. Results. 201 surveyed patients who had undergone SLIT showed PCS-12 of 49.3 (± 7.0) and MCS-12 of 52.6 (± 7.2). These figures correlate strongly with those reported for the German general population (n = 2453): PCS-12 of 49.6 (± 8.7) and MCS-12 of 52.3 (± 8.0). 70.2% (73) of 104 patients were adherent at this practice. Conclusions. QoL in the SLIT patients surveyed here appears as good as that of the general population. Adherence to SLIT at this practice was remarkably better than that reported elsewhere.

Adherence to Sublingual Immunotherapy.

Adherence is a major issue in any medical treatment. Allergen immunotherapy (AIT) is particularly affected by a poor adherence because a flawed application prevents the immunological effects that underlie the clinical outcome of the treatment. Sublingual immunotherapy (SLIT) was introduced in the 1990s, and the early studies suggested that adherence and compliance to such a route of administration was better than the traditional subcutaneous route. However, the recent data from manufacturers revealed that only 13% of patients treated with SLIT reach the recommended 3-year duration. Therefore, improved adherence to SLIT is an unmet need that may be achieved by various approaches. The utility of patient education and accurate monitoring during the treatment was demonstrated by specific studies, while the success of technology-based tools, including online platforms, social media, e-mail, and a short message service by phone, is currently considered to improve the adherence. This goal is of pivotal importance to fulfill the object of SLIT that is to modify the natural history of allergy, ensuring a long-lasting clinical benefit, and a consequent pharmaco-economic advantage, when patients complete at least a 3-year course of treatment.

Aspectos psicosociales en una cohorte de adolescentes con infección por el virus de la inmunodeficiencia humana por transmisión vertical. NeuroCoRISpeS / Psychosocial aspects in a cohort of vertically transmitted human immunodeficiency virus-infected adolescents

INTRODUCCIÓN: Los avances en el tratamiento antirretroviral han mejorado la esperanza de vida de niños con infección por VIH por transmisión vertical. Sin embargo, han aparecido nuevos retos. Planteamos este estudio con el objetivo de determinar los aspectos psicosociales y el conocimiento sobre su enfermedad en una cohorte de adolescentes con infección por VIH por transmisión vertical. MÉTODOS: Se incluyeron pacientes con infección por VIH por transmisión vertical con edades comprendidas entre 12-19 años. Los datos se obtuvieron mediante entrevista semiestructurada y el Strengths and Difficulties Questionnaire para cribado de trastornos emocionales y de conducta. RESULTADOS: Se evaluaron 96 pacientes (58% mujeres) con mediana de edad de 15 años (11-19,1) y mediana de edad del diagnóstico de 1,70 años (0-12,2). La mediana de CD4 en el momento del corte fue 626 céls/mm3 (132-998); el 72% de los pacientes presentaban una carga viral < 50 cop/ml. El 90% asistía al colegio; de ellos, el 60% había repetido algún curso. Conocían su diagnóstico el 81%. Solo el 30% conocía bien su enfermedad y el 18,2% había compartido el diagnóstico con sus amistades. Se detectaron 6 embarazos durante el periodo de estudio. El Strengths and Difficulties Questionnaire mostró riesgo de hiperactividad en el 33%. CONCLUSIÓN: Se objetivan dificultades psicosociales en un elevado porcentaje de pacientes (conocimiento de la enfermedad, relación con pares, fracaso escolar...) que podrían tener impacto en su incorporación a la vida adulta. Son necesarios más estudios para profundizar en el origen y evolución de las dificultades observadas, así como intervenir para prevenir y modificar esta situación

INTRODUCTION: Thanks to advances in antiretroviral treatment, children with HIV infections through vertical transmission have improved their life expectancy. However, new challenges have emerged. We propose this study in order to determine the psychosocial aspects and knowledge of infections in a cohort of adolescents with vertically transmitted HIV infections. METHODS: Patients with vertically-acquired HIV infection between 12 and 19 years old were included. Data were obtained through semi-structured interviews and a Strengths and Difficulties Questionnaire for emotional and behavioral disorders screening. RESULTS: We evaluated 96 patients (58% females) with a median age of 15 years (11-19.1) and a median age at diagnosis of 1.70 years (0-12.2). The median CD4 count was 626 cells/mm3 (132-998), and the viral load was < 50 cp/ml in 72% of patients. Among them, 90% attended school and 60% repeated at least one course. Although 81% of them knew of their diagnosis, only 30% understood their disease, with 18.2% having discussed it with friends. Six unwanted pregnancies occurred during the study period. Strengths and Difficulties Questionnaire showed hyperactivity risk in 33%. CONCLUSION: A high percentage of adolescents show difficulties in several areas (disease knowledge, peer relationship, school failure...) that can have an impact on their adult lives. Further studies are needed to evaluate their origin and development in depth, as well as interventions to modify this situation

The cytological observation of immune adherence of porcine erythrocyte.

The immune adherence (IA) between the porcine erythrocytes and the opsonized Escherichia coli carried green fluorescent protein gene (GFP-E.coli) were detected by the fluorescence microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with an attempt to verify the existence of IA between the porcine erythrocytes and complemented-opsonized microbes. Under fluorescence microscopy, GFP-E.coli opsonized by fresh rabbit serum complement adhered to the erythrocytes and could not be detached by PBS washing, and no IA was observed between the erythrocytes and nonopsonized GFP-E.coli after co-incubation. SEM and TEM also revealed the existence of IA between the serum complement-opsonized GFP-E.coli membrane and the erythrocyte membrane. The partial complement receptor type 1 (CR1)-like gene from porcine was generated by RT-PCR and rapid amplification of cDNA 3' end (3' RACE) (157bp and 578bp), both of which have high similarity with published mammal's CR1 gene. The sequences were spliced based on homology comparison and submitted to GenBank (GenBank Accession No. JX033989). These results indicated that the porcine erythrocytes were able to bind to the opsonized microorganisms. Furthermore, the sequencing results confirmed that the CR1-like gene exists in porcine.

Structural basis for the ABO blood-group dependence of Plasmodium falciparum rosetting.

The ABO blood group influences susceptibility to severe Plasmodium falciparum malaria. Recent evidence indicates that the protective effect of group O operates by virtue of reduced rosetting of infected red blood cells (iRBCs) with uninfected RBCs. Rosetting is mediated by a subgroup of PfEMP1 adhesins, with RBC binding being assigned to the N-terminal DBL1α1 domain. Here, we identify the ABO blood group as the main receptor for VarO rosetting, with a marked preference for group A over group B, which in turn is preferred to group O RBCs. We show that recombinant NTS-DBL1α1 and NTS-DBL1α1-CIDR1γ reproduce the VarO-iRBC blood group preference and document direct binding to blood group trisaccharides by surface plasmon resonance. More detailed RBC subgroup analysis showed preferred binding to group A1, weaker binding to groups A2 and B, and least binding to groups A(x) and O. The 2.8 Å resolution crystal structure of the PfEMP1-VarO Head region, NTS-DBL1α1-CIDR1γ, reveals extensive contacts between the DBL1α1 and CIDR1γ and shows that the NTS-DBL1α1 hinge region is essential for RBC binding. Computer docking of the blood group trisaccharides and subsequent site-directed mutagenesis localized the RBC-binding site to the face opposite to the heparin-binding site of NTS-DBLα1. RBC binding involves residues that are conserved between rosette-forming PfEMP1 adhesins, opening novel opportunities for intervention against severe malaria. By deciphering the structural basis of blood group preferences in rosetting, we provide a link between ABO blood grouppolymorphisms and rosette-forming adhesins, consistent with the selective role of falciparum malaria on human genetic makeup.

Nosocomial transmission of varicella to a healthcare provider positive for anti-varicella zoster virus antibodies: nonprotective positivity with an immune adherence hemagglutination assay.

A 24-year-old male healthcare provider, having attended a varicella patient 2 weeks before, developed varicella himself. He had shown a positive result for anti-VZV antibodies measured with an immune adherence hemagglutination assay (1:4) 1 year before. The present case shows that a positive result with this assay does not necessarily indicate protection against VZV infection.

Performance of an automated solid-phase red cell adherence system compared with that of a manual gel microcolumn assay for the identification of antibodies eluted from red blood cells.

IgG antibodies coating red blood cells (RBCs) can be removed by elution procedures and their specificity determined by antibody identification studies. Although such testing is traditionally performed using the tube agglutination assay, prior studies have shown that the gel microcolumn (GMC) assay may also be used with comparable results. The purpose of this study was to compare an automated solid-phase red cell adherence (SPRCA) system with a GMC assay for the detection of antibodies eluted from RBCs. Acid eluates from 51 peripheral blood (PB) and 7 cord blood (CB) samples were evaluated by both an automated SPRCA instrument and a manual GMC assay. The concordance rate between the two systems for peripheral RBC samples was 88.2 percent (45 of 51), including cases with alloantibodies (n = 8), warm autoantibodies (n = 12), antibodies with no identifiable specificity (n = 2), and negative results (n = 23). There were six discordant cases, of which four had alloantibodies (including anti-Jka, -E, and -e) demonstrable by the SPRCA system only. In the remaining 2 cases, anti-Fya and antibodies with no identifiable specificity were demonstrable by the GMC assay only. All seven CB specimens produced concordant results, showing anti-A (n = 3), -B (n = 1), maternal anti-Jka (n = 2), or a negative result (n = 1). Automated SPRCA technology has a performance that is comparable with that of a manual GMC assay for identifying antibodies eluted from PB and CB RBCs.

Medida de la adherencia al tratamiento antirretroviral / No disponible

No disponible

Modification of solid phase red cell adherence assay for the detection of platelet antibodies in patients with thrombocytopenia.

Platelet refractoriness is caused by HLA antibodies and platelet-specific antibodies. Current methods used to detect antiplatelet antibodies have limitations. Solid phase red cell adherence (SPRCA) lacks sensitivity and requires a second assay using chloroquine-treated intact platelets to specify the response due to anti-HLA. We modified SPRCA by using 2 types of antihuman platelet antibodies with different specificities toward platelet lysate and tested samples from 361 patients (69 with unexplained thrombocytopenia and 292 with poor response to platelet transfusions not explicable by alloimmunization or the clinical situation) and 50 from healthy volunteers. Our method compared favorably with platelet suspension direct immunofluorescence. All samples from healthy volunteers were negative; of the samples from the patient population, 240 were positive (147 samples had only antiplatelet and 3 samples had only anti-HLA antibodies). This modified technique had a sensitivity of 98% and a specificity of 91%.

[Erythrocyte native immune adhering function (ENIAF) in patients with hematopoietic and lymphoid neoplasms and its effect on NK Cell killing activity].

The objective of this study was to investigate the change of native immune adhering function (ENIAF) in self-plasma of patients with hematologic and lymphoid neoplasms and its effect on the killing activity of NK cells. The whole blood was anticoagulated with citric acid. 5 microl precipitated red blood cells and 500 microl plasma of patients or controls were directly mixed with 750 microl quantitative K562 cells at 37 degrees C for 30 minutes. One K562 cell attached by one or more erythrocytes was counted as one rosette, the ratio of rosettes was calculated. Using K562 cells as target cells, the killing activity of NK cells isolated from normal persons was detected by MTT assay, the change of the killing activity was observed after adding RBCs. The results indicated that the ratio of rosettes formed by RBCs of 21 normal controls and K562 cells was 15.3% +/- 6.4%, and the ratio of rosettes formed by RBCs of 24 patients and K562 cells was 7.6% +/- 7.0%. The ability of ENIAF in patients with hematologic and lymphoid neoplasms was significantly lower than that in healthy individuals (t = 3.61, p < 0.001). The killing rate of NK cells in peripheral blood of normal individuals was 67% - 71% without adding RBCs, and it increased by 14.7% +/- 5.2% after adding RBCs of normal controls but decreased by 4.3% +/- 7.6% with RBCs of patients. It is concluded that the ENIAF of RBCs in patients with hematopoietic and lymphoid neoplasms decreases, accompanying the reduction of the killing activity of NK cells to K562 cells, so to detect change of ENIAF may be helpful for the assessment of the immunological function of patients with hematopoietic and lymphoid neoplasms.

PspA and PspC minimize immune adherence and transfer of pneumococci from erythrocytes to macrophages through their effects on complement activation.

Pneumococcal surface protein A (PspA) and PspC are important virulence factors. Their absence has been shown to allow improved clearance of pneumococci from the blood of mice and to decrease pneumococcal virulence. In the presence of antibody and complement, pneumococci attach to erythrocytes in a process called immune adherence (IA), which facilitates their delivery to, and eventual phagocytosis by, macrophages. It is not known, however, if PspA and PspC affect IA. Using PspA and/or PspC isogenic mutants and complement-deficient mouse sera, we demonstrated that absence of PspA allows greater deposition of C1q and thus increased classical-pathway-mediated C3 deposition. In the absence of both PspA and PspC, there is also a major increase in C1q-independent C3 deposition through the alternative pathway. The latter was observed even though absence of PspC alone did not have a major effect on alternative-pathway-dependent complement deposition. The enhanced complement C3 deposition realized in the absence of PspA alone and in the absence of PspA and PspC resulted in both greatly increased IA to human erythrocytes and improved transfer of pneumococci from erythrocytes to phagocytes. These data provide new insight into how PspA and PspC act in synergy to protect pneumococci from complement-dependent clearance during invasive infection.

Alterations in membrane cholesterol cause mobilization of lipid rafts from specific granules and prime human neutrophils for enhanced adherence-dependent oxidant production.

The present study sought to examine the function of membrane lipid rafts in adherence-dependent oxidant production in human neutrophils. Rafts are membrane domains that are rich in glycosphingolipids and cholesterol and are thought to be the foci for formation of signaling complexes in a variety of cells. Disruption of lipid rafts by depletion of membrane cholesterol with the chelating agent methyl-beta-cyclodextrin (MbetaCD) has been widely used to examine the function of lipid rafts. Here, we report that treatment of human neutrophils with MbetaCD unexpectedly caused priming of these cells, manifested as enhanced adherence-dependent oxidant production. Treatment of neutrophils with MbetaCD dose-dependently increased oxidant production after adhesion to fibronectin-coated plates. This priming effect was associated with recruitment of CD11b- and CD66b-rich raft domains from the specific granules, as determined by immunoblot and flow cytometry. Confocal microscopy showed that MbetaCD caused otherwise untreated neutrophils to rapidly adhere and spread on fibronectin-coated plates. Furthermore, three-dimensional reconstruction microscopy studies showed that MbetaCD caused expansion and coalescence of raft domains that covered most of the cell surface. These large raft domains expressed CD11b primarily in the core of these regions. Our studies demonstrate that cholesterol depletion with MbetaCD results in neutrophil priming manifested as enhanced adherence-dependent oxidant production. These studies caution against assumption that any observed MbetaCD effects are a function of reduced raft formation.

Erythrocyte native immune adhering function (ENIAF) in patients with hematopoietic and lymphoid neoplasms and its effect on NK Cell killing activity / 中国实验血液学杂志

The objective of this study was to investigate the change of native immune adhering function (ENIAF) in self-plasma of patients with hematologic and lymphoid neoplasms and its effect on the killing activity of NK cells. The whole blood was anticoagulated with citric acid. 5 microl precipitated red blood cells and 500 microl plasma of patients or controls were directly mixed with 750 microl quantitative K562 cells at 37 degrees C for 30 minutes. One K562 cell attached by one or more erythrocytes was counted as one rosette, the ratio of rosettes was calculated. Using K562 cells as target cells, the killing activity of NK cells isolated from normal persons was detected by MTT assay, the change of the killing activity was observed after adding RBCs. The results indicated that the ratio of rosettes formed by RBCs of 21 normal controls and K562 cells was 15.3% +/- 6.4%, and the ratio of rosettes formed by RBCs of 24 patients and K562 cells was 7.6% +/- 7.0%. The ability of ENIAF in patients with hematologic and lymphoid neoplasms was significantly lower than that in healthy individuals (t = 3.61, p < 0.001). The killing rate of NK cells in peripheral blood of normal individuals was 67% - 71% without adding RBCs, and it increased by 14.7% +/- 5.2% after adding RBCs of normal controls but decreased by 4.3% +/- 7.6% with RBCs of patients. It is concluded that the ENIAF of RBCs in patients with hematopoietic and lymphoid neoplasms decreases, accompanying the reduction of the killing activity of NK cells to K562 cells, so to detect change of ENIAF may be helpful for the assessment of the immunological function of patients with hematopoietic and lymphoid neoplasms.

Screening for platelet antibodies in adult idiopathic thrombocytopenic purpura: a comparative study using solid phase red cell adherence assay and flow cytometry.

BACKGROUND: Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disorder caused by antiplatelet autoantibodies. In this study, we compared 2 methods for screening serum platelet antibodies in patients with ITP. METHODS: A total of 44 adult patients were clinically classified with ITP. We used 2 indirect tests to detect human leukocyte antigen antibodies and/or platelet-specific antibodies in their sera. In method I, we used solid phase red cell adherence (SPRCA) assay. In method II, by flow cytometry, platelets from plateletpheresis components were used as target cells, and fluorescein isothiocyanate-conjugated sheep anti-human IgG Fc was used as the staining reagent. Positive results were defined as any test with the percentage of fluorescence exceeding the reference range by 3% or more in method II. Direct tests detecting platelet-associated IgG on platelets of patients with ITP were done by flow cytometry. RESULTS: Serum specimens from 44 adult patients with ITP (28 female, 16 male) were tested. SPRCA assay could only detect platelet antibodies in 22 patients (50%). By method II, 31 serum specimens (70.5%) yielded positive results. There was a difference between the results of the SPRCA test and method II, with a high degree of significance (p < 0.001) by the McNemar test. No significant difference in platelet counts was observed for patients with and without discernible platelet antibodies by SPRCA assay (p = 0.90). The direct test was positive in 12 patients (66.7%) out of 18 ITP patients tested. CONCLUSION: Flow cytometry is more sensitive than SPRCA assay for detecting platelet antibodies. Detection of platelet antibodies is useful in explaining the immune mechanism and platelet transfusion refractoriness in ITP.