The isotype of autoantibodies influences the phagocytosis of antibody-coated platelets in autoimmune thrombocytopenic purpura

Autoimmune thrombocytopenic purpura (AITP) is an acquired autoimmune bleeding disorder, characterized by isolated thrombocytopenia because of destruction of auto-antibody-coated platelets by Fc-receptor-mediated phagocytosis. The destruction of autoantibody-sensitized platelets by FcγR-bearing phagocytic cells and the following antigen presentation are considered to play a key role for the pathophysiology of AITP. Although different isotypes of AITP-mediating autoantibodies, e.g. IgG, IgM and IgA, are frequently found in AITP patients, their role in the pathophysiology of AITP remains unclear. Using a flow cytometric monocyte-based phagocytosis assay, we investigated the impact of disease-associated autoantibody isotype in antibody-mediated phagocytosis of platelets. Platelets, labelled with 5-chloromethyl fluorescein diacetate (CMFDA), were incubated with AITP patients' serum characterized by pure IgG or IgM antiplatelet autoantibodies. Labelled platelets were incubated with monocytes. Phagocytosis was defined as the product of percentage of CMFDA-positive monocytes and mean fluorescence intensity of CMFDA. Adherence of platelets to monocytes was quantified by anti-CD61-PerCp in a CMFDA(+) CD14(+) gate. IgG-coated platelets showed a significantly higher phagocytic index than IgM-coated platelets (mean 796 ± 157 versus 539 ± 78, P < 0.01). There were no significant differences regarding platelet adherence to monocytes. The isotype of autoantibodies influences the quantity of in vitro phagocytosis of autologous platelets by monocytes. Therefore, the AITP-mediating autoantibody isotype should be considered more carefully in pathophysiologic models and furthermore in diagnostic, therapeutic and prognostic approaches in AITP.

Detection of bacteria in platelet concentrates prepared from spiked single donations using cultural and molecular genetic methods

Bacteria show differences in their growth kinetics depending on the type of blood component. On to storage at 22 degrees C, platelet concentrates (PCs) seem to be more prone to bacterial multiplication than red cell concentrates. Knowledge of the potential for bacterial proliferation in blood components, which are stored at a range of temperatures, is essential before considering implementation of a detection strategy. The efficacy of bacterial detection was determined, using real-time reverse transcriptase-polymerase chain reaction (RT-PCR), following bacterial growth in blood components obtained from a deliberately contaminated whole-blood (WB) unit. Cultivation was used as the reference method. WB was spiked with 2 colony-forming units mL(-1)Staphylococcus epidermidis or Klebsiella pneumoniae, kept for 15 h at room temperature and component preparation was processed. Samples were drawn, at intervals throughout the whole separation process, from each blood component. Nucleic acids were extracted using an automated high-volume extraction method. The 15-h storage revealed an insignificant increase in bacterial titre. No bacterial growth was detected in red blood cell or plasma units. K. pneumoniae showed rapid growth in the pooled PC and could be detected immediately after preparation using RT-PCR. S. epidermidis grew slowly and was detected 24 h after separation. These experiments show that sampling is indicative at 24 h after preparation of PCs at the earliest to minimize the sampling error.

Autologous red cells derived from cord blood: collection, preparation, storage and quality controls with optimal additive storage medium (Sag-mannitol)

To investigate whether packed red cells (PRCs) prepared from autologous cord blood-packed red cells (AC-PRCs) could be used as an alternative for homologous-packed red cells (H-PRCs), we developed a system to collect and prepare AC-PRCs and determined standard storage parameters during 35 days of storage in extended storage medium (Sag-mannitol). We collected and fractionated cord blood from 390 newborns. The amount and quality of the AC-PRCs were analysed. The bacterial contamination rate was 1.84%. Twelve AC-PRCs were stored for 35 days, and standard laboratory parameters were measured at day 1 and day 35. The initial laboratory parameters of the AC-PRCs were similar to the parameters of the H-PRCs. After 35 days, the AC-PRCs displayed an increased haemolysis rate compared to H-PRCs (1.1 versus 0.2%) and also a significant decreased adenosine triphosphate value (1.2 versus 2.3 micromol L(-1)). Haemoglobin, haematocrit and pH were comparable in both groups. AC-PRCs meet the quality criteria for H-PRCs after 35 days. Utilizing a closed collection system for cord blood and an extended storage medium will increase safety and quality and facilitate the routine transfusion of autologous red cells derived from cord blood.

Strategies to reduce perioperative blood loss related to non-surgical bleeding

The treatment of critically ill patients has advanced markedly over the last decade. However, non-surgical bleeding of a diffuse nature from numerous tiny capillaries still remains a challenge. Once initiated, this type of bleeding may be troublesome and a vicious circle develops since it is not a single vessel contributing to this blood loss. The description 'non-surgical blood loss' is often given to this. This review describes a step-by-step approach for the treatment of non-surgical bleeding and includes various measures, such as desmopressin, blood components, antifibrinolytics, antithrombin III, prothrombin complex concentrates and factor XIII. While most non-surgical bleedings can be managed using the approach described here, a number of patients still continue to bleed. In these cases, the surgeon should re-evaluate the bleeding in terms of its surgical origin. If this can positively be excluded and if all of measures described fail to reduce or stop the bleeding, further treatment of such uncontrolled bleeding remains symptomatic.

Quantification of PCR products using microparticles and flow cytometry

The analysis of genetic biomarkers has become an important tool in clinical diagnostics. This includes the identification of disease-related genetic alterations, the detection of pathogenic infective germs on DNA or RNA level and the quantification of the expression of marker genes indicating an altered physiological status. It has been previously described that the combination of polymerase chain reaction (PCR), microparticles and flow cytometry represents a universal platform technology for the routine analysis of such biomarkers. Here we demonstrate the applicability and flexibility of this technology by means of various applications. The quantification of interferon gamma (IFNG) mRNA in irradiated white blood cells is shown as well as the detection of latent infections with cytomegalovirus (CMV). Besides the quantification of single amplification products, the flow cytometric assay is also capable of analysing products of a multiplex PCR. As an example, we describe the identification of spontaneous deletions in the genome of a hybrid cell line using a co-amplified gene (RAB1) essential for the cell survival as an internal control. Furthermore, we show that the use of a green laser (532 nm, 50 mW) substantially increased the sensitivity of the assay compared to conventional flow cytometers using a 488 nm (25 mW) laser. We conclude that the analysis of PCR products using microparticles and flow cytometry fulfils the criteria of clinical routine diagnostics regarding (i) sensitivity, (ii) specificity, (iii) reproducibility and (iv) automatibility.

Tolerance of granulocyte donors towards granulocyte colony-stimulating factor stimulation and of patients towards granulocyte transfusions: results of a multicentre study

Data of 507 granulocyte donations from 183 donors were evaluated. No severe granulocyte colony-stimulating factor (G-CSF)-related side-effects were observed. Three donors complained of severe itching following infusion of hydroxyethyl starch (HES). A high proportion (85%) of the donors stated that they would donate granulocytes again. The mean granulocyte yield was 4.3 x 10(10). High-molecular-weight HES resulted in a significantly higher yield compared with low-molecular-weight HES. Mild, but no severe, adverse transfusion reactions were observed in 16% of the recipients. A leucocyte alloimmunization rate of 24% was found. G-CSF stimulation and transfusion of G-CSF-mobilized granulocytes were well tolerated by donors and recipients, respectively.

A novel true volumetric method for the determination of residual leucocytes in blood components

BACKGROUND AND OBJECTIVES

Accurate determination of residual leucocytes [white blood cells (WBC)] in blood components is of high clinical importance. To date, several labour-intensive, time-consuming or expensive techniques have been used for this purpose.

MATERIALS AND METHODS

A method for the determination of residual WBC is described using a novel low-cost flow-cytometric cell counter and analyser (CCA). The DNA in WBC was stained using 4'-6-diamidino-2-phenylindole (DAPI) and WBC were automatically analysed by true volumetric counting of 200-microl samples (prepared from a 20-microl undiluted sample).

RESULTS

Dilution experiments over a range of 0.5-50 WBC/microl showed a linearity of r = 0.998. The detection limit of this method was 0.83 WBC/microl of red blood cell concentrate (RCC) and 0.67 WBC/microl of platelet concentrate (PC), with an accuracy of 95.5%.

CONCLUSION

Residual WBC (< 1 WBC/microl) can be accurately counted using the CCA within 2 min and at a total cost of less than euro 1 per sample.

HLA-antibody testing: the immune phagocytosis inhibition test is superior to the PRA-STAT and NIH lymphocytotoxic test with respect to specificity

We compared the specificity and sensitivity of four different methods for the detection of antibodies specific for HLA antigens. The NIH version of the complement-dependent cytotoxic test (CDC) was used as the gold standard to which we compared two Fcgamma receptor (FcgammaR)-dependent immune phagocytosis inhibition tests (IPI) and one commercial enzyme-labelled immunosorbent assay (ELISA) with soluble HLA class I-antigen preparations bound to the plate (PRA-STAT). Both IPI tests are based on the fact that HLA-antibodies specifically bind to antigens on the monocyte surface via their Fab portion, and in so doing block a neighbouring FcgammaR with their Fc region. This blockade prevents phagocytosis of IgG-coated red blood cells (RBCs), which can be measured either microscopically (IPIm) or photometrically (IPIp). The four assays were used in blind tests on 20 human alloantisera or monoclonal antibodies with known HLA-antigen reactivities. Additionally, two monoclonal antibodies and one human serum were titrated to elucidate the sensitivity of each test. After all tests were completed, the identities of the samples were disclosed. Both IPI methods detected and identified all clinically relevant HLA class I and class II specific antibodies. In contrast, the CDC was not able to detect noncytotoxic HLA-antibodies and HLA class II specific antibodies; however, it detected clinically insignificant IgM lymphocytotoxins. The PRA-STAT assay enabled identification of all cytotoxic and noncytotoxic IgG antibodies with specificity for HLA-class I antigens. With respect to sensitivity, the CDC and the IPI methods were superior to the PRA-STAT. These facts demonstrate the advantage of IPI methods in the detection of clinically relevant HLA-antibodies.

Platelet glycoprotein complex Ia/IIa antibodies cause neonatal alloimmune thrombocytopenia but do not inhibit megakaryopoiesis and platelet recovery after allogeneic cord blood stem cell transplantation

A sibling cord blood (CB) transplantation was performed in a boy with Wiskott-Aldrich syndrome. The CB (31 x 10(6) CD34(+) cells) derived from a newborn sister with neonatal alloimmune thrombocytopenia (NAIT) with 40,000 platelets/microl, caused by a maternal anti-HPA-5b and HLA-A2 antibody. Maternal serum did not inhibit clonogenicity after in vitro testing of megakaryopoiesis. Accordingly, this CB was accepted for sibling transplantation. The transplantation showed a good course with fast and sustained hematopoietic reconstitution (granulocytes >500/microl on day +16, platelets >50,000/microl on day +30). This case demonstrates a successful CB transplantation from a donor suffering from NAIT.

Kinetics of standardized large volume leukapheresis (LVL) in patients do not show a recruitment phenomenon of peripheral blood progenitor cells (PBPC)

Although several studies have demonstrated the efficacy of large volume leukapheresis (LVL) to yield high numbers of peripheral blood progenitor cells (PBPC), the mechanisms of stem cell release into circulation and the postulated phenomenon of PBPC recruitment during apheresis have not been investigated in detail. Therefore, we analyzed the kinetics of stem cell enrichment in a total of 34 standardized LVL for patients with hematologic malignancies (lymphoma, multiple myeloma) and solid tumors (breast cancer, rhabdomyosarcoma). LVL was started 2 h after administration of G-CSF processing six times the patient's blood volume. Cells were sequentially collected into six bags and the numbers of leukocytes, mononuclear cells (MNC), CD34+ cells and colony-forming cells (CFU-GM) in each collection bag were analyzed. The numbers of PBPC collected demonstrated a continuous decrease starting after an early maximum during the second processed blood volume (P = 0.001). Interestingly, these kinetics of decreasing stem cell yields during LVL were similar for both entities of patients with hematologic malignancies as well as for both groups of patients with solid tumors. In summary, a recruitment phenomenon, defined as a time-dependent and LVL-induced increase of PBPC, could not be demonstrated in any of the diseases investigated.

Automated serological compatibility testing using a solid-phase test and standard laboratory equipment

BACKGROUND AND OBJECTIVES

To prove the feasibility of a semi-automated cross-match procedure using a commercially available solid-phase microplate test and standard laboratory equipment.

MATERIAL AND METHODS

The new procedure was evaluated against the conventional spin tube technique and the gel centrifugation system.

RESULTS

The sensitivity of the method and the rate of non-specific reactions were equal to those for the other test systems. The samples taken from the red cell concentrates for cross-matching remained stable for the shelf-life of the product.

CONCLUSION

The semi-automated cross-match was successfully introduced in our routine laboratory as a means to process large numbers of tests.

Polymorphisms in the non-coding region of the human mitochondrial genome in unrelated plateletapheresis donors

Human mitochondrial DNA polymorphisms are unique targets to discriminate nucleated cells and platelets between donor and recipient in the setting of transplantation or transfusion. We have previously used this approach to discriminate allogeneic platelets from autologous platelets after transfusion. In the present study, we used DNA sequencing to investigate polymorphisms present in two of the hypervariable segments (HVR1 and HVR2) found within the non-coding region of the mitochondrial genome among 100 plateletapheresis donors. Alignments were made with the Cambridge Reference Sequence (CRS) for human mitochondrial DNA (mtDNA). Combining the sequencing information of HVR1 and HVR2 we could demonstrate that, of the 100 investigated mtDNA samples, none was identical to the CRS. We found a total of 2-17 polymorphisms per donor in the investigated regions, most of them were basepair substitutions (563) and insertions (151). No deletions were found. Sixty-six of the 110 detected polymorphisms were detected in more than one sample. Seven polymorphisms are newly described and have not been published in the Mitomap database. Our results demonstrate that polymerase chain reaction analysis of the many polymorphisms found in the hypervariable region of mitochondrial DNA represents a more informative target than previously described mitochondrial polymorphisms for discriminating donor-recipient cells after transfusion or transplantation.

Simultaneous immunomagnetic CD34+ cell selection and B-cell depletion in peripheral blood progenitor cell samples of patients suffering from B-cell non-Hodgkin's lymphoma

The reduction of residual tumor cells is one of the main targets of leukapheresis product (LP) processing. Immunomagnetic enrichment/selection of CD34+ progenitor cells (Baxter Isolex 300i) can achieve a reduction of contaminating B-cells of approximately 2-3 logs in B-cell non-Hodgkin's lymphoma patients. Specific release of the enriched CD34+ cells (stem cell releasing agent PR34+; Baxter) and the use of antibody-coated immunobeads targeted against B-cell markers (CD10, CD19, CD20, CD22, CD23, and CD37) during this procedure allows the GMP-like simultaneous capture of residual B cells within a closed system. This combination of two purging techniques enhances the B-cell depletion capacity up to 4.5 logs. By performing 10 clinical-scale purging procedures, we could show that the simultaneous immunomagnetic purging method is easy to perform and highly efficient. We evaluated B-cell log depletion by flow cytometry for cases with marker-positive cells detectable before and after the purging procedure. The mean reduction of B-cells in these cases was 3.5 logs; the mean CD34+ cell yield and purity were 47 and 92%. Using three LPs, we tested the procedure on a modified Baxter Isolex 300i device with software adaptations for this procedure (software version 2.0) in direct comparison with CD34+ cell selection only, using the former version (version 1.12). The CD34+ cell yield was 49% (40-54%) for the CD34+ cell selection and 51% (19-72%) for simultaneous double selection. The mean purity was 96% for CD34+ cell selection and 98% for simultaneous double selection. B-cell depletion was 1.9 logs for CD34+ cell selection, and after simultaneous double selection, the B-cell content was decreased by 3.7 log steps (P = 0.0495). Clinical application of double-purged cells has not prolonged the hematopoietic recovery times after high-dose therapy as compared with nonpurged peripheral blood progenitor cell autotransplants. In conclusion, we could show that the simultaneous double selection protocol developed leads to a highly increased B-cell purging efficacy when compared with CD34+ cell selection without any negative effects regarding CD34+ cell yield and engraftment times after high-dose therapy.

Volume-dependent collection of peripheral blood progenitor cells during large-volume leukapheresis for patients with solid tumours and haematological malignancies

We investigated the efficacy of peripheral blood progenitor cell (PBPC) collection during large-volume leukapheresis (LVL) in patients with solid tumours and haematological malignancies (n = 18). The time- and volume-dependent harvest of leucocytes (WBC), mononuclear cells (MNC), CD34+ cells and colony-forming cells (CFU-GM) during LVL was analysed in six sequentially filled collection bags processing four times the patient's blood volumes. The amounts of leucocytes (WBC) and the purity of mononuclear cells (MNC%) did not show any significant changes during LVL. The percentage of CD34+ cells remained constant for the first three bags but consecutively decreased from initially 1.71% CD34+ cells in the beginning of LVL to finally 1.34% CD34+ cells (P = 0.02). The mean numbers of colony-forming cells (CFU-GM) decreased from 74 microL-1 to 59 microL-1 during LVL (P = 0.16). Furthermore, the comparison of volume-dependent PBPC collection for patients with high, medium and low total yields of CD34+ cells showed similar kinetics on different levels for the three groups. We concluded that - relative to the initial total amount of PBPC harvested - comparable numbers of progenitor cells can be collected during all stages of LVL with a slight decreasing trend processing four times the patient's blood volumes.

Efficacy and safety of simultaneous immunomagnetic CD34+ cell selection and breast cancer cell purging in peripheral blood progenitor cell samples used for hematopoietic rescue after high-dose therapy

We have established a new simultaneous positive/negative selection procedure using the Baxter Isolex 300i system. We tested its tumor cell (TC) purging efficacy by tumor contamination tests ex vivo and its safety in a group of 17 breast cancer (BC) patients by measuring hematopoietic recovery after high-dose (HD) therapy and autologous stem cell rescue with the selected cells. Tumor contamination tests resulted in a TC depletion of 4.1-6.0 log steps. The CD34+ cell yield in this experimental setting was 38.9-91.5%, and the CD34+ cell purity was 86.0-96.0%. In a group of 17 BC patients (5 high-risk adjuvant, > or = 10 lymph nodes positive, and 12 metastatic), we processed leukapheresis products (LPs) by simultaneous positive/negative selection. In these clinical samples, the mean CD34+ cell yield was 56.2% (range, 14.0-80.1%), and the CD34+ cell purity was 94.5% (range, 69.0-99.8%). Additionally, we screened samples of the patients' LPs before and after the purging procedure for contaminating TC by immunocytochemistry. In 15 of 17 tested cases, TCs were detectable prior to the purging procedure. After the procedure, we could not detect residual TCs in 16 of 17 cases. In one case, we found a highly reduced number of TCs. Furthermore, we evaluated the times for hematopoietic reconstitution in a group of five BC patients in the high-risk adjuvant situation who underwent HD chemotherapy and hematopoietic rescue with positive/negative selected stem cells and compared it with our own data from 10 BC patients who, after identical HD therapy, received only positively selected CD34+ cells and 14 patients who, after identical HD therapy, received autografts purged by incubation with toxic ether lipids (ET-18-OCH3). In all groups, a leukocyte count of >2000 cells/microl was reached at day +10. A platelet count of > 50,000 cells/microl was reached at day +12 in the ET-18-OCH3 group and at day +14 in the other two groups. Furthermore, 12 patients with metastatic disease rescued with positive/negative selected stem cells after HD therapy also showed fast and comparable hematopoietic recovery. The new simultaneous immunomagnetic positive/negative selection using a closed system is effective and safe. Processing LPs leads to a similar CD34+ cell yield, a higher TC depletion compared to standard CD34+ cell selection, and no delay in hematopoietic recovery.

[Peripheral blood stem cell transplantation as an interdisciplinary challenge--theory and practice]

High dose chemotherapy with consecutive autologous peripheral blood stem cell transplantation becomes increasingly important for the treatment of hematological diseases and solid tumors. A complete remission or at least a prolonged survival can be achieved for numerous malignant diseases by an intensification of chemo- and radiotherapy. Therefore, the autologous peripheral blood stem cell transplantation (PBSCT) represents an elementary precaution to reduce the therapy-associated aplasia by administration of hematopoietic precursor cells. Both, high dose chemotherapy with consecutive PBSCT demands great clinical experience and the collection, processing and positive selection of blood stem cells is a challenge for the Transfusion Medicine. Correct handling and utilization of blood stem cells for clinical and laboratory purposes (e.g. positive selection) must be guaranteed, since each restriction of the function of processed blood stem cells may lead to an insufficient engraftment after PBSCT. Therefore, the clinical divisions of the University Hospital Münster are planning and practising peripheral blood stem cell transplantations in cooperation with the Department of Transfusion Medicine. The collection, processing and quality control are performed by the Department of Transfusion Medicine in close contact with the other clinical departments, who subsequently perform high dose chemotherapy and peripheral blood stem cell transplantations.

Inflammatory mediators in bronchoalveolar lavage fluid and plasma in leukocytopenic patients with septic shock-induced acute respiratory distress syndrome

OBJECTIVES

The acute respiratory distress syndrome (ARDS) is a frequent complication of severe sepsis and a major cause of death in patients with hematologic malignancy during chemotherapy-induced leukocytopenia. Inflammatory mediators are important modulators of host response to injury and have been found to be increased in the bronchoalveolar lavage (BAL) fluid of nonleukocytopenic patients with ARDS. Since inflammatory cytokines in plasma of nonleukocytopenic patients seem to be efficient predictors of the course of ARDS, we examined this hypothesis in leukocytopenic patients with septic shock-induced ARDS.

DESIGN

Prospective, observational study.

SETTING

Intensive care unit (ICU) of a university hospital.

PATIENTS

Nineteen patients with leukocytopenia (white blood cell count of <1/nL) following cytoreductive chemotherapy for malignant disorders and severe sepsis with shock-induced ARDS (Murray score of >2.5).

INTERVENTIONS

BAL and plasma sampling and ICU management.

MEASUREMENTS AND MAIN RESULTS

The proinflammatory cytokines tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-8 were measured in the BAL aspirates and in plasma samples, both obtained within 18 hrs after onset of ARDS. Hemodynamic and oxygen metabolism data were measured immediately before plasma samples were taken and BAL was performed. Of the 19 patients studied, nine patients responded to ICU treatment (e.g., mechanical ventilation as indicated by PaO2/FIO2, FIO2, shunt volume, and course of pulmonary infiltrates), whereas ten patients did not respond. BAL cytokine concentrations were significantly increased in nonresponders in comparison with responding patients (TNF-alpha, p = .021; IL-6, p = .008; IL-8, p = .019). In contrast, we did not observe any differences between the groups in terms of plasma cytokine concentrations.

CONCLUSION

Determination of cytokine concentrations in BAL samples may be useful for evaluation of severity and course of ARDS in leukocytopenic patients, whereas measurement of plasma cytokines is not helpful.

The influence of different erythrocyte lysing procedures on flow cytometric determination of CD34+ cells in umbilical cord blood transplants

Since the correct determination of CD34+ cells is of great clinical importance for successful transplantation with haematopoietic progenitor cells (HPCs) from cord blood, we investigated the influence of different erythrocyte lysing techniques on the quantification of CD34+ cells in umbilical cord blood. Flow cytometric determinations of CD34+ cells were performed from 20 cord blood samples, using three different erythrocyte lysing procedures and two monoclonal CD34 antibodies (n = 360). Flow cytometric analysis showed characteristic patterns of the forward (FSC) and side (SSC) scatter light properties for the leucocyte subsets for each of the investigated erythrocyte lysing procedures, indicating that these reagents cause different morphological changes on leucocytes. Furthermore, significant differences of CD34+ cell counts were obtained for identical samples using different lysing techniques (P = 0.001 and P = 0.002). In some cases, a more than 100% difference was found comparing different erythrocyte lysing procedures. In contrast, the determination of CD34+ cells by two CD34 antibodies showed a good reproducibility without significant differences between both antibodies for each of the erythrocyte lysing techniques. We conclude that the erythrocyte lysing procedure represents a very critical and important step for accurate determination of CD34+ cells in whole blood samples. Especially for the quantification of HPCs in cord blood transplants, this influence may be of high clinical relevance.

Suppression of panel-reactive antibodies by treatment with mycophenolate mofetil

"Panel Reactive Antibody" (PRA) testing is commonly used to assess the pretransplant antibody status in order to estimate the risk of an adverse humoral response following transplantation. We report on a female patient with end-stage cardiac failure suffering from acute myocarditis who underwent implantation of a left-ventricular assist device (Novacor, Baxter Healthcare Corp. Oakland, CA). During evaluation for heart transplantation, a PRA level of 50-70% was detected. After treatment with mycophenolate mofetil at a dosage of 2 g daily, PRA levels declined within one week to 0-5%, and remained low after discontinuation of the immunosuppressive drug. We feel that pretreatment of patients with elevated PRA levels with mycophenolate mofetil is well justified.

Flow cytometric analysis of protein phosphorylation in the hematopoetic system

Cellular growth and differentiation in blood cells are regulated by the phosphorylation status of growth factor receptors and downstream proteins. Protein kinases and phosphatases balance the homeostasis of protein phosphorylation. Various diseases are associated with alterations in these tightly regulated processes. Aberrations have been proved to be of diagnostic value and might enhance the pathophysiological insight into the origin of the disease. However, quantitation of protein phosphorylation is currently not feasible in a clinical situation. We developed a flow cytometric methodology which enables for direct investigation of protein phosphorylation in cell populations defined by multi-color flow cytometry. This assay does not only overcome drawbacks of traditional methodologies (e.g. Western blotting) but also allows quantitative analyses even in rare cell populations. We accurately examined phosphorylation levels in different cell populations of hematological interest and especially analyzed CD34+ hematopoietic progenitor cells. CD34+ cells in bone marrow and in cord blood contained similar, low levels of phosphotyrosine. Circulating pheripheral blood system cells PBSC in patients exposed to G-CSF for stem cell mobilization exhibited significantly increased levels of phosphotyrosine. In vitro exposure of CD34+ progenitors to growth factors (G-CSF, IL-3, SCF) raised the levels of tyrosine phosphorylation in bone marrow and cord blood. Effects were dose and time dependent. Interestingly, in vivo stimulated CD34+ PBSC could not be further stimulated in vitro. In conclusion, we present a new powerful methodology for analysis of protein phosphorylation in hematological specimens. The method does not only allow for accurate detection of phosphorylation levels in vivo, but also enables for quantitative analysis of growth factor receptor stimulation in vitro and in vivo.

[Enzyme immunoassay for the determination of serotonin in stored platelet concentrates]

A new enzyme immunoassay (EIA) was applied on measurements of serotonin (5-HT) in stored platelet concentrates (PC). PC were prepared by apheresis of two separators (Cobe, Fresenius) or from buffy coats and stored for a period of 7 days at 22 degrees C and agitating. Measurements were done in pellets and suspension medium (plasma). Detection of 5-HT was specific and sensitive within the bounds of 2 and 1,000 ng/10(9) PLT.

[Measurement of alloreactive anti-recipient helper T-cell precursors after allogenic bone marrow transplantation]

Acute graft-versus-host disease (GvHD) is a severe complication after allogenous bone marrow transplantation (BMT). The compatibility of major histocompatibility complex antigens (MHC) is the strongest stimulus for GvHD, which also occurs in patients with a genetically MHC-identical sibling donor. In such cases it would be helpful to recognize anti-recipient (interleukin-2-producing) T-lymphocyte precursors to detect a minor histocompatibility antigen (mH), which escapes from typing methods. To quantitate the alloreactive immune response initiating acute GvHD, we established the helper T-lymphocyte precursor test (HTL-p) as described by Theobald et al. in 'GvHD direction', using a limiting dilution assay. Serial dilutions of the donor peripheral blood mononuclear cells (PBMCs) were cultured for 14 days with constant numbers of stimulator PBMCs from the recipient, followed by an unspecific restimulation step with phytohemagglutinin (PHA) or specific restimulation with EBV-transformed blast cells from the recipient. The Il-2 production of specific T cells was assessed by addition of CTLL-16 cells, whose proliferation was measured by an ELISA. We suppose that the HTL-p test is a good tool for measuring the number of anti-recipient T-lymphocyte precursors as a predictive value for the intensity of GvHD.

Active uptake of serotonin as viability parameter of stored platelets

The platelet-plasma serotonin (5-HT) exchange in different apheresis products and platelet concentrates (PCs) from buffy coats was studied for quality control over a period of 7 days. In PCs with steadily decreasing pH due to inappropriate gas exchange the platelet 5-HT concentration increases significantly (> 10% positive netto uptake) during the 1st day of storage. Thereafter platelet serotonin drops rapidly with t1/2 = 1 day at pH < 6.5, but platelet counts were constant and 5-HT uptake was inhibited concomitantly. Plasma 5-HT increases as pH decreases. This can be enforced by competitive inhibition of serotonin uptake due to imipramine which also moderates the total 5-HT loss. However, in PC with stable pH the operative 5-HT pump keeps steady-state conditions. The efficacy of the transmembrane uptake mechanism can be adequately monitored by the assessment of the 5-HT platelet/plasma ratio as a new platelet viability parameter.

Detection of HLA antibodies by an enzyme-linked photometric immune phagocytosis inhibition test

The immune phagocytosis inhibition test (IPI) has been described as a sensitive method for the detection of cytotoxic and non-cytotoxic HLA antibodies. We performed a photometric IPI and compared this technique with the conventional microscopic IPI. In further investigations we used the photometric IPI in comparison with the lymphocytotoxicity test (LCT) for the detection of HLA antibodies. The photometric IPI showed a high correlation to the microscopic IPI. In tests with different known HLA antibodies the photometric IPI reached a sensitivity of 85.1% versus 80.5% in the LCT, and a specificity of 92.3 versus 100% in the LCT. Diluted patient sera showed a higher sensitivity in the photometric IPI. We conclude that the photometric IPI can be used as a convenient and sensitive technique for the detection of HLA antibodies.

Efficacy and kinetics of bone marrow processing and enrichment of haematopoietic progenitor cells (HPC) by a large-volume apheresis procedure

We investigated the efficacy of bone marrow (BM) processing by an automated large-volume apheresis procedure (6 x original BM volume) in 10 paediatric and adult patients undergoing BM harvesting before myeloablative therapy. Volume-dependent kinetics during apheresis were analyzed by sequential collection of processed cells into a six-fold collection bag system with consecutive analysis of the single bags. BM processing resulted in an 83.3% (+/- 21) recovery of mononuclear cells (MNC), a 97.9% (+/- 1.1) reduction of erythrocytes (RBC) and a 87.7% (+/- 2.9) volume reduction. To determine volume-dependent kinetics of haematopoietic progenitor cell (HPC) enrichment during apheresis, leukocytes (WBC), mononuclear cells (MNC), CD34 cells and colony-forming cells (CFU-GM) were serially quantitated in subsequent collection bags. Large-volume BM processing significantly enhanced absolute yields of CD34+ cells (mean: 4.01 (+/- 2.81) x 10(6)/kg bw) and CFU-GM (mean: 1.92 (+/- 1.47) x 10(4)/kg bw) compared with the standard procedure (3 x BM volume) by 26.9% (+/- 10.9) and 27.2% (+/- 11.6), respectively. We concluded that large-volume apheresis for BM processing is an efficient technique significantly improving the yields of haematopoietic progenitor cells (HPC) without any relevant changes in the purity of the final product. Moreover, sequential collection and analysis of HPC represents a good model to investigate the volume-dependent kinetics and efficacy of BM processing.

Effect of storage conditions on the CD34+ counts in flow cytometric analysis after anticoagulation of samples with EDTA

The transplantation of peripheral blood precursor cells (PBPC) is becoming of interest for autografting patients with a wide variety of haematological and other malignancies. For rapid quality control of PBPC apheresis products, flow cytometry is applied to quantify the number of CD34+ events. We studied the effect of different storage conditions on the number of CD34+ counts in EDTA-anticoagulated aliquots of PBPC grafts. Within 24 h, CD34+ signals decreased when samples were stored at room temperature (RT, 20 +/- 2 degrees C) compared to the results obtained directly after cytapheresis. The signal rate equalled or exceeded the baseline values after 24 h when aliquots were deposited at room temperature and subjected to agitation. Storage at 4 degrees C revealed no significant changes. These data indicate that quality control of PBPC samples by flow cytometry significantly depends on storages time, temperature and other conditions like the agitation of the specimen.

Rapid quantitative analysis of protein tyrosine residue phosphorylation in defined cell populations in whole blood and bone marrow aspirates

We developed a rapid method for quantification of tyrosine phosphorylation in immunophenotypically defined cell populations in specimens of whole blood and unprocessed bone marrow. Samples were formaldehyde-fixed and cells were permeabilized. Phosphotyrosine residues and surface antigens were simultaneously stained by monoclonal antibodies and visualized by flow cytometry. The accuracy of the method was confirmed by demonstration of an increase of phosphotyrosine levels in pp60v-src transformed fibroblasts. In blood of healthy donors, monocytes and granulocytes showed higher levels of phosphotyrosine than lymphocytes. CD34+ peripheral blood stem cells showed slightly increased tyrosine phosphorylation compared to autologous lymphocytes. Significantly elevated levels of phosphotyrosine were demonstrated in leukaemic blasts compared to lymphocytes (P = 0.01).

[Functional evaluation of erythrocytic antibodies by photometric detection of erythrophagocytosis in the monocyte monolayer assay]

In haemolytic disease of newborn (erythroblastosis fetalis) the in vivo behaviour of erythrocytic IgG antibodies is of particular significance. The monocyte monolayer assay (MMA), which determines by microscopy the number of erythrocytes phagocytosed by monocytes, is an important functional test for the qualitative assessment of erythrocytic IgG antibodies. We set up a photometric MMA and compared it with the microscopic MMA. In both tests we employed commercially available rhesus antibody sera and examined 8 sera of pregnant women with mild and severe courses of haemolytic disease of newborn by the photometric MMA. Good agreement was found between the microscopic and photometric MMA (r = 0.93). Over and above this the photometric MMA correlated with the course of haemolytic disease of newborn in 7 out of 8 cases (with one false-positive finding). The photometric technique permits rapid, sensitive and reproducible determination of erythrophagocytosis in microtitre plates. This method is based on the photometric detection of haemoglobin of phagocytosed erythrocytes via a peroxidase reaction. Standardised photometric MMA could in future be more widely applied especially in haemolytic disease of newborn for the functional characterisation of erythrocytic antibodies, the incidence of intra-assay and inter-assay errors being low.

Improved automated bone marrow processing and enrichment of CD34+ cells by a large-volume apheresis procedure

We investigated the efficacy of bone marrow (bm) processing by a large-volume apheresis procedure using a self constructed sixfold collection bag system for sequential cell collection and analysis for 5 pediatric patients. Quantitation of leukocytes (WBC), CD34+ cells and colony-forming cells (CFU-GM) within the single bags showed a relative time-dependent decrease of all cell fractions during leukapheresis, whereas the relative amount of mononuclear cells (MNC) droped only slightly. At the same time the large volume apheresis (6 x original bm-volume) clearly enhanced the absolute yield of CD34+ cells compared to the standard procedure (3 x bm-volume) for more than 20%. We conclude that large-volume apheresis for bm processing is an efficient technique to improve the yields of progenitor cells.