In vitro quantification of anti-red blood cell antibody production in idiopathic autoimmune haemolytic anaemia: effect of mitogen and cytokine stimulation.

The immunopathogenic mechanisms underlying idiopathic autoimmune haemolytic anaemia (AIHA) are still unknown, although regulatory cytokines are thought to play an important role. We investigated cytokine production by mitogen-stimulated whole blood cultures from 21 patients with AIHA and from 22 age- and sex-matched controls. In parallel experiments, we studied the effect of mitogen and cytokine stimulation on anti-red blood cell (RBC) IgG antibody production, assessed as both binding on autologous RBCs and secretion in culture supernatants. To quantify anti-RBC antibody, we set up a sensitive and quantitative solid phase competitive immunoassay. The results showed that in AIHA patients production of interleukin (IL)-4, IL-6 and IL-13 was significantly increased, whereas that of interferon (IFN)-gamma was reduced. Multivariate analysis showed that IFN-gamma was the only independent factor significantly associated with the reduced T-helper-1-like cytokine profile. Patients with active haemolysis showed further reduction of IFN-gamma and IL-2 production and increased secretion of transforming growth factor (TGF)-beta. In AIHA patients, mitogen stimulation, as well as IL-6, significantly increased autologous anti-RBC-binding relative to unstimulated cultures. Mitogen stimulation and addition of IL-4, IL-6, IL-10, IL-13 and TGF-beta significantly increased both autologous anti-RBC binding and antibody secretion in AIHA patients compared with controls. The results suggest that a reduced T-helper-1- and a predominant T-helper-2-like profile and elevated TGF-beta levels might play a role in the immunopathogenesis of AIHA. Furthermore, our competitive anti-RBC antibody was able to detect anti-RBC antibody production in some direct antiglobulin test (DAT)-negative AIHA patients.

Use of IgM monoclonal reagents licensed for tube tests in column agglutination technology.

BACKGROUND: Red cell (RBC) phenotyping using column agglutination technology (CAT) is currently limited by the reagents formulated in the system. To overcome this limitation, it was investigated whether monoclonal IgM reagents licensed for use with tube tests produced valid results with CAT. STUDY DESIGN AND METHODS: Commercial CAT, does not contain antisera, was used to evaluate Procedures A (40 microL of reagent and 10 microL of 4% RBCs) and B (50 microL of reagent and 50 microL of 0.8% RBCs) with or without incubation at room temperature. In Study 1, reagents were tested to determine whether potentiators inhibit the passage of antigen-negative RBCs through the column. In Study 2, CAT sensitivity was measured by the use of potency titrations to define a procedure for each reagent that matched or exceeded that of the tube method. In Study 3, the specificity of each reagent was determined in parallel with the CAT and tube tests. Typing of 1644 samples was performed. RESULTS: Study 1: Free passage was obtained with all reagents. Study 2: Immediate-spin methods using CAT produced the same results as the tube method. Study 3: With 8048 comparisons made, discrepant results were found in 32 transfused patients and in 6 cord blood samples, mainly with Lewis reagents. With comparison of CAT and the standard tube method, complete agreement was obtained with Kell reagents, 99.9-percent agreement with Kidd reagents, and 98.9-percent and 99.4-percent agreement with Lewis reagents. CONCLUSION: Most examined reagents seem suitable for use with CAT.

Evaluation of a new automated instrument for pretransfusion testing.

BACKGROUND: A number of automated devices for pretransfusion testing have recently become available. This study evaluated a fully automated device based on column agglutination technology (AutoVue System, Ortho, Raritan, NJ). STUDY DESIGN AND METHODS: Some 6747 tests including forward and reverse ABO group, Rh type and phenotype, antibody screen, autocontrol, and crossmatch were performed on random samples from 1069 blood donors, 2063 patients, and 98 newborns and cord blood. Also tested were samples from 168 immunized patients and 53 donors expressing weak or variant A and D antigens. Test results and technician times required for their performance were compared with those obtained by standard methods (manual column agglutination technology, slide, semiautomatic handler). RESULTS: No erroneous conclusions were found in regard to the 5028 ABO group and Rh type or phenotype determinations carried out with the device. The device rejected 1.53 percent of tests for sample inadequacy. Of the remaining 18 tests with discrepant results found with the device and not confirmed with the standard methods, 6 gave such results because of mixed-field reactions, 10 gave negative results with A2 RBCs in reverse ABO grouping, and 2 gave very weak positive reactions in antibody screening and crossmatching. In the samples from immunized patients, the device missed one weak anti-K, whereas standard methods missed five weak antibodies. In addition, 48, 34, and 31 of the 53 weak or variant antigens were detected by the device, the slide method, and the semiautomated handler, respectively. Technician time with the standard methods was 1.6 to 7 times higher than that with the device. CONCLUSION: The technical performance of the device compared favorably with that of standard methods, with a number of advantages, including in particular the saving of technician time. Sample inadequacy was the most common cause of discrepancy, which suggests that standardization of sample collection can further improve the performance of the device.

Use of photografting technique for the immobilization of blood-grouping antibodies onto microtiter plates.

Commercial anti-A, anti-B, anti-A,B and anti-D monoclonal and polyclonal antisera were immobilized onto polystyrene microtiter plates using a photografting technique, to set up a new solid-phase assay (SPA) to be used for blood grouping. The reactivity and specificity of each grafted antisera were studied using red blood cells (RBCs) expressing normal and weak antigens. The stability of immobilized antisera was also studied. After dry storage of plates at +4 degrees C, room temperature, and +37 degrees C, SPA was performed using fresh and/or frozen RBCs. The same test was carried out after storing plates under protective conditions. Concordance of collected with expected results was obtained in all cases when the SPA was performed using monoclonal antisera and RBCs, with normal or weak expression of ABO and D antigens immediately after plate preparation or after dry storage at +4 degrees C. Plates stored dry at room temperature or at +37 degrees C gave inconsistent results, whereas a slight increase in reactivity was observed after storage under protective conditions. The specificity and the reactivity of tested antibodies were not modified by the immobilization procedure, not even after dry storage at +4 degrees C. Damage produced by water evaporation during dry storage in hard conditions could be reduced by adding a protective solution to microtiter wells at the beginning of storage.

A micro colorimetric assay using cryopreserved monocytes to evaluate antibody-mediated red cell-monocyte interaction.

BACKGROUND AND OBJECTIVE: A number of in vitro assays based on the interaction of red cells with monocytes have been used to determine the clinical significance of red cell antibodies. When used in our laboratory, one of these assays (the monocyte-macrophage phagocytosis assay-MMPA), was very time consuming and showed great variability. METHODS: We set up a monocyte phagocytosis colorimetric assay (MPCA), using standard microtiter plate wells coated at 37 degrees C for 1 hour with monocytes from healthy donors. After washing the wells to remove non-adherent monocytes, test red cells are added to the wells. Sensitized red cells bind to the monocytes, which are lysed after incubation to measure red cell phagocytosis. This is done by hemoglobin detection in the lysate through reaction with o-phenylenediamine and absorbance evaluation with a colorimeter. The results are expressed as the phagocytosis index (PI), which is calculated with the following formula: PI = [1-(A450 unsensitized red cells/A450 sensitized red cells)] x 100. In this study we determined: the source of MPCA variability; the precision of MPCA results; the correlation between MMPA and MPCA results; the MPCA reference values and the MPCA and MMPA execution times. RESULTS: MPCA variability depended largely on the monocyte source. The smallest variation coefficient of the results of replicate assays (19-21%) was found using pooled, cryopreserved monocytes. When performed with a pool of cryopreserved monocytes from 10 subjects, the SD of PI values obtained in replicate assays showed little variation (11-13) over the range of anti-D concentrations tested (from 18.75 to 300 ng/mL). A linear correlation coefficient r of 0.96 was obtained when MPCA and MMPA were performed in parallel, and the 95th centile of PI reference values determined with red cells of 40 non-transfused surgical patients free of irregular red cell antibodies was 7. MPCA execution time was 56% of that needed to perform MMPA. INTERPRETATION AND CONCLUSIONS: These studies show that MPCA is an easy and reproducible assay which allows objective and automated evaluation of red cell phagocytosis.

ABO genotyping in Italian blood donors.

BACKGROUND: Traditional ABO blood group serology is based on the immunoreactivity of antisera with the carbohydrate A, B and H antigens. Progress in the molecular biology of the ABO system has recognized the molecular basis of the red cell (RBC) antigens and has provided a genetic model for ABO polymorphism at the molecular level. Recently, this genetic model was tested in a large number of individuals. MATERIALS AND METHODS: In this study we applied DNA analysis to determine the frequency of ABO genotypes in a group of blood donors for whom the ABO type was known. Two hundred and fifty healthy Italian blood donors were analyzed using polymerase chain reaction (PCR) to amplify two different regions of genomic DNA, each of which contained a different nucleotide polymorphism. The amplified product was digested with 4 restriction enzymes that revealed differences among A, B and O individuals. To analyze the genes at polymorphic sites 261 and 703 we used the restriction enzymes BstE II and Kpn I, and Hpa II and Alu I and compared the PCR determined genotypes to serologically determined phenotypes. RESULTS AND CONCLUSIONS: The results were consistent for all unrelated individuals; however, 2 of 100 individuals with the 0 phenotype carried one allele that differed from the proposed genetic model. This novel O allele, termed 0(2) by Yamamoto et al., was found in our series with a frequency of 1%. The blood group AB0 genotype of 250 healthy Italian blood donors was: 13 AA/AO(2), 37 AO(1), 11 BB, 39 B0(1), 50 AB, 98 0(1)0(1) and 2 0(1)0(2). This method should be applicable not only in forensic medicine but also in immunohematology when serology fails.

Reactivity of 62 Rh MAbs with weak and variant antigens.

We characterized serologically 5 anti-C (4 IgM and 1 IgG), 3 anti-c (2 IgM and 1 IgG), 4 anti-E (1 IgM and 3 IgG), 4 anti-e (3 IgM and 1 IgG) and 46 anti-D (16 IgM and 30 IgG) monoclonal antibodies, provided by the Rh Section of the Third International Workshop and Symposium on Monoclonal Antibodies against Human Red Blood Cells and Related Antigens (1996) for their ability to detect weak and variant antigens. The agglutination patterns were established using untreated and papain-treated red blood cells in a column agglutination technology system (BioVue, Ortho). Significant differences were found between the IgM and IgG antibodies. The papain treatment seemed to be important for IgM but not for IgG antibodies. Almost all of the IgM anti-D antibodies detected untreated DIV samples and almost all of the IgG anti-D antibodies detected untreated weak D samples. Both IgM and IgG anti-D antibodies showed the highest number of negative reactions with DVI and Rh 33 red blood cells. The CwCw sample was detected by only one of the 4 anti-C IgM MAbs using enzyme-treated red blood cells. All anti-c MAbs were able to detect treated Cx samples. Because of the small number of weakly expressed E and e samples, definitive conclusions cannot be drawn on the ability of these antibodies to detect these antigens.

Red cell alloantibodies in thalassemia major. Results of an Italian cooperative study.

Clinical and serological data on 1435 Italian thalassemia major patients were collected during a cooperative study involving 19 centers in 10 regions. The main findings were as follows: 18 percent of the patients were under 6 years of age, 63 percent between 6 and 15, and 19 percent over 15. Forty-one percent had undergone splenectomy. Sixty-two percent of the patients were maintained at pretransfusion hemoglobin levels higher than 10 g per dl, 36 percent between 8 and 10 g per dl, and 2 percent below 8 g per dl. Overall, 5.2 percent of the patients had clinically significant red cell alloantibodies (136 alloantibodies in 74 patients). One-half of the immunized patients had more than one and one-fourth had more than two alloantibodies. The specificities of the 136 alloantibodies were almost exclusively confined to the common antigens of the Rh, Kell, Kidd, and Duffy systems, in that decreasing order of frequency. The antibody screening procedure, using a low-ionic-strength solution antiglobulin test against a three-red-cell panel and the patient's own red cells (autocontrol) with a serum to cell ratio of 100 to 1 was shown to be an adequate technique for red cell antibody detection.

Preparation of leukocyte-free platelets for transfusion by filtration through cotton wool.

Filtration through Imugard filters of random platelet concentrates or platelets obtained by plateletpheresis allow the preparation of leukocyte-free platelets for transfusion. The procedure is simple and determines only a small platelet loss (less than 10%). Filtered platelets seem to function normally in vivo. The use of leukocyte-free red cell and platelet transfusions for the support of patients suffering from leukemia or aplastic anemia could prevent major complications, such as refractoriness to platelet transfusion and to bone marrow transplantation.

Effectiveness of red blood cells filtered through cotton wool to prevent antileukocyte antibody production in multitransfused patients.

The effectiveness of red blood cells made leukocyte-free by filtration through cotton wool to prevent the production of antileukocyte antibodies was evaluated in children suffering from Cooley's anemia. Two studies were performed: study I was carried out prospectively in two groups of non transfused patients, one group treated with leukocyte-free filtered red cells, the other with buffy-coat-free packed red cell units. Different types of antileukocyte antibodies were looked for in both groups and the results were compared. In study II the behavior of pre-existing lymphocytotoxic antibodies found in the serum of children previously transfused with standard or buffy-coat-free packed red cell units was followed after the patients had been passed to a program of transfusion with leukocyte-free filtered red cells. Study I showed that none of the patients transfused with leukocyte-free filtered red cell units have produced antileukocyte antibodies, while these could be found in 2/3 of the patients transfused with buffy-coat-free packed red cell units. Study II showed that the repeated transfusion of leukocyte-free filtered red cells to patients who possessed in their serum preformed lymphocytotoxic antibodies did not cause any increase in the potency or spectrum of these antibodies, but was in fact accompanied in some cases by their decrease or disappearance. It is concluded that filtration through cotton is an easy and inexpensive means of preparing leukocyte-free red blood cells for transfusion capable of preventing (or reducing) the production of antileukocyte antibodies in multitransfused patients.