Quantitation of red cell-associated IgG using an immunoradiometric assay

Diagnostic algorithm for classification and characterization of direct antiglobulin test-negative autoimmune hemolytic anemia with 1-year clinical follow-up

BACKGROUND

Approximately 5%-10% of autoimmune hemolytic anemia (AIHA) cases are negative for direct antiglobulin test (DAT). We previously reported a classification system for untreated patients with DAT-negative AIHA by quantifying levels of red blood cell (RBC)-bound IgG. This study investigated the clinical utility of a novel diagnostic algorithm with a comprehensive classification system and characterized each subgroup in DAT-negative AIHA.

STUDY DESIGN AND METHODS

We assessed 637 patients with undiagnosed hemolytic anemia using our diagnostic algorithm and classification system, which was based on RBC-bound IgG levels and results of column method-DAT before and after washing RBCs.

RESULTS

Patients were diagnosed with DAT-negative AIHA with 97% sensitivity and 84% specificity when the laboratory tests were performed before treatment and classified into the following six categories: tube DAT-negative, low-affinity IgG, double DAT-negative, IgA- or IgM-positive, low-affinity IgM, and s/o non-AIHA. The first three types were major conditions and accounted for 76% of DAT-negative AIHA cases. Based on multivariate analyses of idiopathic DAT-negative AIHA (n = 71), platelet count and albumin concentration were significant factors for survival at 1-year follow-up. The low-affinity IgG group showed the highest platelet count and albumin levels, better response to steroids, and higher 1-year survival rate than those in other groups.

DISCUSSION

Our classification included DAT-negative, IgA-driven, and warm-IgM AIHA categories, which were atypical forms of AIHA with the severe onset and increased risk of relapse. When treating a patient with DAT-negative hemolysis, atypical AIHA should be considered and tested in reference laboratories, especially before treatment.

Band 3 ectopic expression in colorectal cancer induces an increase in erythrocyte membrane-bound IgG and may cause immune-related anemia

Autoimmune hemolytic anemia (AIHA) is a rare comorbidity in colorectal cancer (CRC) and has an unknown etiology. Previously, we described an AIHA case secondary to CRC with ectopic band 3 expression. Herein, we investigated ectopic band 3 expression and erythrocyte membrane-bound IgG in a CRC cohort. Between September 2016 and August 2018, 50 patients with CRC and 26 healthy controls were enrolled in the present study. The expression of band 3 and SLC4A1 mRNA was observed in 97% of CRC surgical specimens. Although clinical AIHA was not observed in any patient with CRC, a direct antiglobulin test was positive in 10 of the patients in the CRC group (p = 0.01). Flow cytometry revealed significantly increased erythrocyte membrane-bound IgG among patients with CRC compared to healthy controls (mean ± standard deviation; 38.8 ± 4.7 vs. 29.9 ± 15.6, p = 0.012). Normocytic anemia was observed, including in cases negative for fecal occult blood, suggesting a shortened erythrocyte life-span due to increased membrane-bound IgG. Immunoprecipitation revealed increased anti-band 3 autoantibodies in patients' sera. Mouse experiments recapitulated this phenomenon. We also confirmed that band 3 expression is controlled by 5'AMP-activated protein kinase under hypoxic conditions. These findings increase our understanding of the etiology of cancer-related anemia.

Utilisation of Flow-cytometry in the Diagnosis of Auto Immune Haemolytic Anaemia

Auto Immune Haemolytic Anaemia (AIHA) is one of the most common types of acquired haemolytic anaemias. Its main cause is auto-antibody mediated rapid destruction of Red Blood Cells (RBCs). Demonstration of a positive Direct Antiglobulin Test also known as Coomb's test, against these autoantibodies is the crucial serological assay in the diagnosis of AIHA. This routinely used test has the disadvantage of low sensitivity and does not detect low levels of red cell auto antibodies leading to false negative results sometimes. Flow cytometry can effectively diagnose such patients with low levels of autoantibodies. This study was carried out in a tertiary care center, where patients with suspected AIHA were studied during 2 years period. Blood samples of suspected patients of AIHA were tested by both Gel Card Test and by Flow-cytometry for detection of RBC bound IgG. A total of 50 patients with suspected diagnosis of AIHA were studied by flow-cytometry as well as by Gel card test for detection of RBC bound IgG. Out of these 50 cases, 41 cases have turned out to be positive and 9 were negative by flow-cytometry. By Gel card test, out of 50 cases, 34 were positive and 16 were negative. Therefore, there were 7 cases which were negative for RBC bound IgG by Gel card test and these were positive by flow-cytometry. Flow-cytometry is a reliable and more sensitive method and can be used as a new routine diagnostic technique for AIHA.

How do we diagnose immune thrombocytopenia in 2018?

In this report, we will review the various clinical and laboratory approaches to diagnosing immune thrombocytopenia (ITP), with a focus on its laboratory diagnosis. We will also summarize the results from a number of laboratories that have applied techniques to detect anti-platelet autoantibodies as diagnostic tests for ITP. Although there is considerable variability in methods among laboratories, there is general agreement that platelet autoantibody testing has a high specificity but low sensitivity. This suggests several possibilities: (1) the ideal test for ITP has yet to be developed, (2) current test methods need to be improved, or (3) ITP is the clinical expression of a variety of thrombocytopenic disorders with different underlying mechanisms. Even the clinical diagnosis of ITP is complex, and experienced clinicians do not always agree on whether a particular patient has ITP. Improvements in the diagnostic approach to ITP are necessary to improve the management of this disorder.

Diagnosis and management of newly diagnosed childhood autoimmune haemolytic anaemia. Recommendations from the Red Cell Study Group of the Paediatric Haemato-Oncology Italian Association

Autoimmune haemolytic anaemia is an uncommon disorder to which paediatric haematology centres take a variety of diagnostic and therapeutic approaches. The Red Cell Working Group of the Italian Association of Paediatric Onco-haematology (Associazione Italiana di Ematologia ed Oncologia Pediatrica, AIEOP) developed this document in order to collate expert opinions on the management of newly diagnosed childhood autoimmune haemolytic anaemia.The diagnostic process includes the direct and indirect antiglobulin tests; recommendations are given regarding further diagnostic tests, specifically in the cases that the direct and indirect antiglobulin tests are negative. Clear-cut definitions of clinical response are stated. Specific recommendations for treatment include: dosage of steroid therapy and tapering modality for warm autoimmune haemolytic anaemia; the choice of rituximab as first-line therapy for the rare primary transfusion-dependent cold autoimmune haemolytic anaemia; the indications for supportive therapy; the need for switching to second-line therapy. Each statement is provided with a score expressing the level of appropriateness and the agreement among participants.

Characterization of direct antiglobulin test-negative autoimmune hemolytic anemia: a study of 154 cases

Direct antiglobulin test (DAT)-negative (DAT-)autoimmune hemolytic anemia (AIHA) is empirically thought to show the same clinical conditions as DAT-positive (DAT+)AIHA, with the exception of an adequate amount of red blood cell (RBC)-bound immunoglobulin (Ig)G. We investigated the clinical characteristics of DAT-AIHA in comparison with DAT+AIHA. Of the 582 patients referred to our laboratory with undiagnosed hemolytic anemia, AIHA was clinically diagnosed in 216 patients (DAT-AIHA, n = 154; DAT+AIHA, n = 62). The percentage of reticulocytes, mean corpuscular volume, RBC-IgG levels, white blood cell count, and total protein (TP) levels were significantly higher in patients with DAT+AIHA than patients with DAT-AIHA. The hemoglobin level was significantly lower in patients with DAT+AIHA. No significant differences between patients with DAT-AIHA and DAT+AIHA existed with respect to age, gender, idiopathic/secondary nature, complications such as Evans syndrome, effectiveness of steroid treatment, or survival rate at 1 year following diagnosis. Patients with DAT-AIHA required significantly lower doses of steroids for maintenance therapy. Based on multivariate analysis of idiopathic DAT-AIHA (n = 110), TP and Evans syndrome were associated with the effectiveness of steroids (adjusted odds ratio [aOR], 1.36/[0.1 g/dl]; 95% confidence interval [CI], 1.01-1.84) and survival at the 1-year follow-up (aOR, 0.1; 95% CI, 0.01-0.88). Our results indicate that patients with DAT-AIHA generally suffer milder anemia and hemolysis than patients with DAT+AIHA, respond equally well to steroids, and have comparable survival at 1-year.

Management of blood donors and blood donations from individuals found to have a positive direct antiglobulin test

The medical literature is replete with articles addressing the diagnosis and management of patients with a positive direct antiglobulin test (DAT). However, there is scant information addressing the management of blood donors and blood donations found to have a positive DAT. Practices vary considerably between countries and blood suppliers within countries, and there is no standardized approach to the management of these blood donors or the blood products prepared from their donations. Recent evidence from Israel suggests that the finding of a positive DAT in a blood donor may not be as benign as previously thought. Therefore, it may be prudent for blood collection agencies to periodically reexamine their approach to the management of blood donors with a positive DAT and their donations. This article reviews the available literature and explores options for the management of DAT-positive blood donors and their blood donations.

Low concentration of serum haptoglobin has impact on understanding complex pathophysiology in patients with acquired bone marrow failure syndromes

To clarify whether measurement of serum haptoglobin (Hp) has impact on understanding pathophysiology in bone marrow failure (BMF) syndromes, we investigated concentrations of serum Hp by nephelometric procedure in 156 Japanese patients with BMF, including 54 aplastic anemia (AA), 50 paroxysmal nocturnal hemoglobinuria (PNH), and 52 myelodysplastic syndromes (MDS) patients. The frequencies with low concentrations of serum Hp (<42 mg/dL) in PNH patients (98.0%) were significantly higher than those in AA (27.8%; P < 0.0001) and MDS (38.5%; P < 0.0001) patients. In AA patients, white blood cell (WBC), absolute neutrophil, and platelet counts were significantly decreased in the group (n = 15) with low concentrations of serum Hp than in that (n = 39) with normal concentrations of it, and WBC counts were positively correlated with concentrations of serum Hp, suggesting that WBC counts may affect the concentrations. In MDS patients, hemoglobin concentrations and serum iron were significantly decreased and increased, respectively, in the group (n = 20) with low concentrations of serum Hp than in that (n = 32) with normal concentrations of it, and the values of serum iron were inversely correlated with concentrations of serum Hp, suggesting that ineffective erythropoiesis may affect the concentrations. Several AA and MDS patients with low concentrations of serum Hp had Coombs-negative autoimmune hemolytic anemia determined by immunoradiometric assay. In conclusion, several factors in conjunction with pathophysiology contribute to decrease of serum Hp in BMF.

Transient myelofibrosis with autoimmune pancytopenia: a case report

INTRODUCTION

Myelofibrosis associated with myelodysplasia is thought to herald poor prognosis in myelodysplastic syndrome (MDS).

CASE REPORT

A 7-month-old boy presented with fever (39 degrees C), pancytopenia, and slight hepatosplenomegaly (3 and 2 cm, respectively). Bone marrow showed hypercellularity, hyperplasia of erythroblasts, and also myelofibrosis. IgG was 1,136 mg/dL, IgA was 131 mg/dL, and IgM was 89 mg/dL. Antinuclear and antineutrophil antibodies, red-blood-cell-associated IgG, antiplatelet antibodies, and Coombs test were positive. Karyotype was 46XY. No viral cause was evidenced. Mild myelodysplasia was revealed two months later, but was insufficient to support a diagnosis of MDS. The boy was treated with transfusion of packed cells, prednisolone 2 mg/kg/day for 3 weeks associated with intravenous gammaglobulin 400 mg/kg/day for 5 days. Direct Coombs remained positive 1 month after treatment for 5 months, myelofibrosis persisted for 3 months, and neutropenia for 21 months. After 3-year follow-up, hematological data were normal without any therapeutic intervention.

CONCLUSION

Myelofibrosis associated with mild myelodysplasia and pancytopenia can have a benign evolution in infants and young children.

Clinical application of a flow cytometric direct antiglobulin test

BACKGROUND

The clinical application of flow cytometric direct antiglobulin test (FC-DAT) has rarely been evaluated for patients with various diseases including immune and nonimmune hemolytic anemia.

STUDY DESIGN AND METHODS

Blood samples from 380 patients with a variety of diseases were studied using the tube direct DAT and FC-DAT. The results of tube DAT and FC-DAT were compared. The predictive values of DAT for hemolysis were evaluated.

RESULTS

Of 57 patients with autoimmune hemolytic anemia (AIHA), 6 of the 17 with a negative tube DAT (immunoglobulin G [IgG]) had a positive FC-DAT (IgG) and 23 of the 36 patients with a negative tube DAT (complement 3d [C3d]) had a positive FC-DAT (C3d). In 57 patients with AIHA, the incidence of positive results of FC-DAT (IgG) and tube DAT (IgG) were similar (42 positive vs. 40 positive); but in 323 patients without AIHA, the incidence of positive FC-DATs (IgG) was higher than that of tube DAT (IgG; 47 positive vs. 9 positive). The higher incidence of positive FC-DAT (C3d) than that of tube DAT (C3d) was seen in patients with AIHA (42 positive vs. 21 positive) as well as in patients without AIHA (61 positive vs. 5 positive). Both DAT (IgG) and DAT (C3d) positive has highest positive predictive value for hemolysis, followed by DAT (IgG) alone positive and DAT (C3d) alone positive.

CONCLUSIONS

FC-DAT is a complementary test for diagnosing AIHA. There is a synergistic effect of the red blood cell-bound IgG and complement in predicting hemolysis.

Cut-off value of red-blood-cell-bound IgG for the diagnosis of Coombs-negative autoimmune hemolytic anemia

Direct antiglobulin test (DAT)-negative autoimmune hemolytic anemia (Coombs-negative AIHA) is characterized by laboratory evidence of in vivo hemolysis, together with a negative DAT performed by conventional tube technique (CTT) in clinically suspected AIHA patients. The immunoradiometric assay (IRMA) for red-blood-cell-bound immunoglobulin G (RBC-IgG) can be used to diagnose patients in whom CTT does not detect low levels of red cell autoantibodies. We investigated the diagnostic cutoff value of the IRMA for RBC-IgG in Coombs-negative AIHA and calculated its sensitivity and specificity. Of the 140 patients with negative DAT by CTT referred to our laboratory with undiagnosed hemolytic anemia, AIHA was clinically diagnosed in 64 patients (Coombs-negative AIHA). The numbers of Coombs-negative AIHA and non-AIHA patients changed with age and gender. The cutoff values were determined from receiver operating characteristic (ROC) curve according to age and gender. The IRMA for RBC-IgG proved to be sensitive (71.4%) and specific (87.8%) when using these cutoffs. Using these cutoffs for 41 patients with negative DAT referred to our laboratory in 2006, all the pseudonegative cases were treated with steroids before the test. The 31 untreated cases could be grouped using one cutoff value of 78.5 and showed 100% sensitivity and 94% specificity, independent of gender and age. Results indicate that RBC-IgG could become a standard approach for the diagnosis of Coombs-negative AIHA, when measured before treatment.

Immune hemolytic anemia associated with negative routine serology

Immune hemolytic anemia can occur in patients who have no antibodies detectable by routine procedures (direct [DAT] and indirect [IAT] antiglobulin tests). DAT-negative autoimmune hemolytic anemias (AIHAs) represent 5% to 10% of all AIHAs. Three causes have been identified: (1) small numbers of red blood cell (RBC)-bound IgG molecules below the threshold of the DAT; (2) IgA and IgM autoantibodies; and (3) low-affinity autoantibodies. Antibody-independent cytotoxic events caused by natural killer (NK) cells have also been implicated. DATs are sometimes found to be positive when tested by reference laboratories, due to poor technique in reading antiglobulin tests in hospital laboratories. Hemolytic transfusion reactions also can occur when no alloantibodies are detectable by routine procedures. In some cases antibodies can be detected by special serologic procedures (such as the Polybrene test); in other instances phenotypically matched RBCs survive well and a specific antigen can be shown to be involved, suggesting a specificity (like anti-C) that is undetectable by any technique. Antibodies other than to blood group antigens, such as human leukocyte antigen (HLA) antibodies, may sometimes be involved.

Direct-antiglobulin-test-negative immune haemolytic anaemia and thrombocytopenia in a patient with Hodgkin's disease

A case of direct-antiglobulin-test (DAT)-negative auto-immune haemolytic anaemia (AIHA) and immune thrombocytopenia (ITP) associated with Hodgkin's disease (HD) is reported. A 52-year-old male was admitted with anaemia, thrombocytopenia, and lymphadenopathy. The patient was DAT negative, although he exhibited the clinical features of warm-type AIHA and elevated levels of red-blood-cell-associated IgG (RBC-IgG). The serum level of platelet-associated IgG (PA-IgG) was markedly increased. A biopsy specimen of the inguinal lymph nodes showed HD of mixed cellularity. Marked improvement of subjective symptoms, normalization of haematological values and a decrease in the level of both RBC- and PA-IgG were observed after the start of combination chemotherapy for HD. Although the association of HD, ITP, and/or AIHA has been infrequently reported, the measurement of RBC-IgG is recommended in cases of HD with anaemia even though DAT is negative, since HD is known to be associated with various protean immunological abnormalities.

Reactivity of autoantibodies of autoimmune hemolytic anemia with recombinant rhesus blood group antigens or anion transporter band3

The specificity of autoantibodies in autoimmune hemolytic anemia (AIHA) has been studied using the serological procedure and immunoprecipitation technique with rare phenotype red cells. We attempted to analyze specificity using recombinant rhesus (Rh) blood group and band3 antigens expressed on erythroleukemic cell lines, KU812E. The autoantibody eluates were isolated by the acid elution procedure from the red cells of 20 AIHA patients. The recombinant Rh antigens, RhD, cE, ce, CE, and chimera antigens CE-D and D-CE, were obtained by retroviral cDNA transduction into KU812E cells, and the cell line expressing the antigens was cloned. Band3 cDNA was also obtained and introduced into KU812E and cloned KU812 expressing RhcE. The reactivities of AIHA eluates with recombinant Rh and band3 antigens were studied by flow cytometry. Fifteen eluates reacted with at least one of the RhcE, ce, or CE antigens, and four eluates reacted with RhD. Seven eluates with strong Rh specificity were studied further using chimera antigen. Five eluates showed reduced or lost reactivity, although two eluates reacted identically with the chimera antigens as wild type. These results indicated that conformational epitopes constituted by RhD or CE specific exofacial peptide loops are important for autoantibodies in most cases. Seven eluates reacted with band3, five exclusively. The coexpression study of RhcE and band3 did not enhance the expression of either antigen nor the reactivity with patient eluates, indicating that association of Rh and band3 was not involved in the appearance of autoantigen.

Abnormal proliferation of CD4- CD8+ gammadelta+ T cells with chromosome 6 anomaly: role of Fas ligand expression in spontaneous regression of the cells

We report a case of granular lymphocyte proliferative disorder accompanied with hemolytic anemia and neutropenia. Phenotypes of the cells were T cell receptor gammadelta+ CD3+ CD4- CD8+ CD16+ CD56- CD57-. Southern blot analysis of T cell receptor beta and gamma chains demonstrated rearranged bands in both. Chromosomal analysis after IL-2 stimulation showed deletion of chromosome 6. Sorted gammadelta+ T cells showed an increase in Fas ligand expression compared with the levels in sorted alphabeta+ T cells. The expression of Fas ligand on these gammadelta+ T cells increased after IL-2 stimulation. The patient's anemia improved along with a decrease in granular lymphocyte count and disappearance of the abnormal karyotype without treatment. The expression of Fas ligand may be involved in spontaneous regression of granular lymphocyte proliferation with hemolytic anemia.

Human Rh monoclonal antibodies: assessment of functional activity by chemiluminescence and RhD antibody quantitation

In vitro cellular assays have been described which are capable of evaluating the interactions between sensitised red cells and monocyte or K cells. The chemiluminescence assay (CL) has several advantages over other cellular assays used to assess functional activity. The CL assay unlike the ADCC assays does not require the use of radioisotopes and therefore can be easily integrated into the work of a Reference Serology laboratory. The CL assay is an objective test and not labour intensive which is the main criticism of the monocyte monolayer assay. Seventy-four monoclonal anti-Ds and 29 other Rh specificities have been evaluated by a CL assay. The use of the chemiluminescent response produced by erythrophagocytosis of sensitised red cells has been shown to correlate well with the in vivo response to red cells sensitized with polyclonal IgG antibodies. This study aimed at investigating whether the CL assay could identify and differentiate monoclonal antibodies that are capable of eliciting a response from human monocytes. Poor correlation was obtained between the CL assay results and anti-D quantitation (r = 0.236). The chemiluminescence assay discriminated between anti-D's with high quantitation levels but low predicted functional activity and anti-Ds of low quantitation levels which produced elevated CL responses. Only 3 of the 29 non-Rh D specificities tested produced a response in the CL assay emphasising the importance of specificity in the functional activity of monoclonal antibodies. The demonstration of significant differences in the functional capabilities of monoclonal antibodies has important implications for reviewing the possible use of monoclonal anti-D preparations for Rh immune prophylaxis and highlights the requirement for factors other than the antibody concentration to be examined.

An enzyme-linked antiglobulin test to quantify nanogram quantities of IgG on polystyrene microspheres

A method is described in which polystyrene latex beads are used for constructing standard curves to estimate the number of protein molecules on cell surfaces by an enzyme-liked immunoassay test (ELAT). A series of immune globulin (IgG) dilutions in pH 9.8 carbonate buffer were coated on 3-microns microbeads by incubation overnight at 4 degrees C and subjected to ELAT. The r value of the curve derived from four assays was 0.9991. This standard curve applied to previously recorded ELAT data resulted in estimating that normal RBC have 63 +/- 19 (SD) IgG molecules and that the lower level of sensitivity of the antiglobulin test is 155 IgG molecules per RBC. The method should be useful for more precise standardization of procedures for measuring proteins on cell surfaces.

Quantification of IgG on erythrocytes of patients and normals by a radio-ligand-binding assay

A monoclonal IgG anti-human IgG, 1B12, was used in a radio-ligand-binding assay to quantify IgG on erythrocytes of patients and normals. The assay detected a range of 10-700 IgG molecules. Good correlation was achieved between the number of molecules and the strength of agglutination in antiglobulin tests performed in capillary tubes. The assay was capable of detecting subagglutinating immune bound IgG on erythrocytes from patients with systemic lupus erythematosus (SLE).

In vitro sequestration of erythrocytes from hosts of various ages

Erythrocytes from young and old human donors were separated according to age-density on Stractan gradients. Old donors had more low age-density (young) erythrocytes than did young donors. Levels of IgG bound to old and young erythrocytes were determined by ELISA. Erythrocytes from old donors bore higher levels of IgG on their erythrocytes (123 +/- 55 IgG molecules per young RBC and 196 +/- 43 IgG per old RBC) than did those from young donors (58 +/- 15 IgG per young RBC and 98 +/- 20 IgG per old RBC). In an in vitro erythrophagocytosis assay, young and old erythrocytes from old donors and old erythrocytes from young donors were shown to be recognized and phagocytosed by lymphokine activated human peripheral blood monocytes. Young erythrocytes from young donors were not phagocytosed in this assay. The in vitro erythrophagocytosis of erythrocytes from old and young donors can be specifically blocked by beta-galactoside but not alpha-galactoside sugars. This phagocytosis is not blocked by Protein-G which specifically blocks Fc-gamma mediated erythrophagocytosis of Rh-D+ erythrocytes coated with IgG anti-Rh-D antibodies. beta-galactoside and alpha-galactoside sugars have no inhibitory effect on erythrophagocytosis mediated by IgG anti-Rh-D antibodies coating Rh-D+ erythrocytes. It thus appears that erythrophagocytosis of young and old erythrocytes from old donors and old erythrocytes from young donors are all mediated by a lectin-like receptor on the monocytes which recognizes beta-galactoside-like sugar moiety on the erythrocytes rather than by recognition of IgG on the erythrocyte and an Fc receptor on the macrophage. It also appears that the membrane of both young and old erythrocytes of old donors are marked for phagocytosis whereas only the old erythrocytes from young donors are so marked.

Characterization of senescent red cells from the rabbit

The above data continue to demonstrate the metabolic well being of the aged red cell as it is isolated from rabbits. The abundance of ATP, the absence of surface-bound IgG and a variety of other observations at this time lead to the tentative conclusion that the senescent red cell is amazingly healthy. Many investigators have predicted that the red cell is removed from the circulation as a metabolically exhausted effete cell. There is currently no evidence to support this other than a decrease in deformability of the cells with time, but it is not clear that this decline in deformability is sufficient to keep the cell from circulating. In either case, many of the previously proposed causes of cellular removal are clearly incorrect for the rabbit, and it is now time to focus on new directions for observing either cellular impairment or perhaps the presence of a cellular clock which is independent of the cell's metabolic state. Another point which should be addressed is the reliability of the biotinylation model in rabbits as it relates to red cells in other species. So far several observations in aged red cells isolated with valid models have been reproduced across species boundaries including the rise in ATP, the fall in AMP deaminase activity, the shift in the 4.1a to 4.1b protein ratio, the stability of a number of glycolytic enzymes, and the instability of pyrimidine 5'-nucleotidase activity. To this point, the rabbit has been a reliable model of red cell aging and one with implications for other species.

Characterization of autoantibodies in mixed-type autoimmune hemolytic anemia

Three of 46 patients with autoimmune hemolytic anemia (AIHA) satisfied the diagnostic criteria for mixed-type AIHA in which both warm-type and cold-type autoantibodies against red blood cells (RBCs) are present. The specificities of these autoantibodies were analyzed. All of the warm-type autoantibodies were IgG-chi, and the specificities were not serologically classified. The autoantibody of patient 1 reacted to the 41- and 80-kD peptides on immunoblotting, and the epitope corresponding to it was papain sensitive. Two warm-type autoantibodies from patients 2 and 3 resembled each other in serological analyses and reacted with a protease- and neuraminidase-resistant antigen. However, the antigen corresponding to the autoantibody of patient 3 was located on the 37-kD peptide by immunoprecipitation. All of the cold-type autoantibodies were IgM-cha and showed high titer and high thermal amplitude. According to the reaction pattern with untreated and enzyme-treated RBCs, the cold-type autoantibodies of patients 2 and 3 were revealed to be anti-Om and anti-I, respectively. In patient 1, the cold-type autoantibody was characterized as having high affinity for autologous RBCs, but its specificity was unclassified. The antigens corresponding to the cold-type autoantibodies were not located by immunoblotting and immunoprecipitation. These serological and immunochemical approaches to autoantibodies in mixed-type AIHA revealed that the warm and cold components recognized the different antigens.

Passive haemagglutination inhibition for quantitation of red cell associated IgG

Passive haemagglutination inhibition (PHI) was adapted to quantitate red cell associated IgG. Twenty one patients with autoimmune haemolytic anaemia (AIHA) had a raised red cell associated IgG, mean (SD) = 5.783 (6.183) ng/10(6) red blood cell compared with that of 69 subjects with a red cell associated IgG of 0.433 (0.349) ng/10(6) red blood cell. Thirteen of 14 blood donors with a positive direct antiglobulin test (DAGT) had a normal red cell associated IgG. The only blood donor with positive DAGT and raised red cell associated IgG had AIHA. Studies of red cell associated IgG in other groups of patients were also undertaken. The technique is simple, does not require the use of sophisticated equipment, and is suitable as a routine test in hospital laboratories. The results of red cell associated IgG by PHI are reproducible and clinically relevant.

Impaired reticuloendothelial function in patients treated with methyldopa

In about 20 per cent of patients taking the antihypertensive agent methyldopa, IgG autoantibodies form against red cells, but most such patients do not have hemolysis. The reason for this is uncertain; it does not appear to be explained by known characteristics of the autoantibody. Since antibody-dependent reticuloendothelial function is an important determinant of cell clearance, we measured reticuloendothelial function in nine patients taking methyldopa. We did this by measuring the rate of clearance of radiolabeled autologous red cells sensitized with anti-D alloantibody. Five patients had a positive direct antiglobulin test, and four did not. Only one patient had laboratory evidence of hemolysis. The patients without hemolysis had significantly impaired reticuloendothelial clearance. In contrast, the patient with hemolysis did not have impaired reticuloendothelial function. This study suggests that in patients taking methyldopa who have a positive direct antiglobulin test the absence of hemolysis may be caused by an impairment in reticuloendothelial function. That the drug itself may be responsible for the impairment is suggested by the occurrence of abnormal reticuloendothelial function in patients taking the drug who have a negative direct antiglobulin test.

Follow-up of normal individuals with a positive antiglobulin test

Over a period of 20 yr (1962-1982), 67 apparently fit donors at a Regional Blood Transfusion Service were found to have an unexplained positive direct antiglobulin test (DAT). During 1983, 26 were traced and re-tested. 9 still had a positive DAT only 1 of whom had developed autoimmune haemolytic anaemia. 17 had become negative though in 7 of these an autoantibody could still be detected by an enzyme technique. Unlike patients with established autoimmune disorders, the positive DAT individuals were found to have normal T cell subsets though B cells were significantly increased.