Instrumented PVP-augmented antiglobulin tests. I. Detection of allogeneic antibodies coating otherwise normal erythrocytes

ABO hemolytic disease of the newborn: a need for clarity and consistency in diagnosis

The diagnosis of ABO hemolytic disease of the newborn (ABO HDN) has been the subject of considerable debate and clinical confusion. Its use as an overarching default diagnosis for hyperbilirubinemia in all ABO incompatible neonates regardless of serological findings is problematic and lacks diagnostic precision. Data on hemolysis indexed by carbon monoxide (CO) levels in expired air (ETCOc) and blood (COHbc) support an essential role for a positive direct antiglobulin test (DAT) in making a more precise diagnosis of ABO HDN. A working definition that includes ABO incompatibility, significant neonatal hyperbilirubinemia, and a positive DAT is needed to gain clarity and consistency in the diagnosis of ABO HDN. Absent a positive DAT, the diagnosis of ABO HDN is suspect. Instead, a negative DAT in a severely hyperbilirubinemic ABO incompatible neonate should trigger an exhaustive search for an alternative cause, a search that may require the use of targeted gene panels.

Autoimmune haemolytic anaemia in childhood associated with non-complement binding IgM autoantibodies

Red cell bound IgM autoantibodies free of associated IgG autoantibodies and unable to activate complement have not yet been considered as the cause of autoimmune haemolytic anaemia (AIHA). We report on warm type AIHA resulting from the action of IgM autoantibodies on circulating RBC. Twelve children (eight of whom were infants) with relatively severe haemolytic anaemia were studied. Whereas the clinical findings and courses of all children appeared to be compatible with warm type AIHA, the serological findings during the haemolytic phase were atypical in that the direct antiglobulin test (DAT) was negative in 11, and positive in one case due to C3d only. The use of radiolabelled antihuman globulin antibodies showed, however, that the RBC of all the patients were sensitized with warm IgM antibodies. Elevated values of IgA and/or IgG immunoglobulins on the patients' RBC were found to be present in only two cases. Complement activation by IgM autoantibodies could not be detected in all other cases neither in vivo nor in vitro. Thus, we conclude that non-complement binding IgM autoantibodies were responsible for the AIHA in the majority of these children possibly representing an as yet unrecognized variant of warm type AIHA.

Hemolytic anemia due to a mixture of low-titer IgG lambda and IgM lambda agglutinins reacting optimally at 22 degrees C

A 65-year-old white man had severe hemolytic anemia due to a mixture of low-titer IgG lambda and IgM lambda agglutinins showing optimum reactivity at 22 degrees C. The IgG agglutinins were detected by manual indirect antiglobulin test (IAT) using anti-IgG, and had a titer of 1 at 37 degrees C, 128 at 22 degrees C and 16 at 4 degrees C against adult type O red blood cells (RBC). The corresponding titers with cord RBC were 1 (37 degrees C), 64 (22 degrees C) and 8 (4 degrees C). Proteolytic enzyme and neuraminidase treatment of RBC did not decrease these titers. No known specificity could be assigned to these agglutinins. The isolated agglutinins (recovered by cold adsorption, warm elution) were shown by immunoelectrophoresis to be IgG lambda antibodies. They did not bind complement in vitro, consistent with the finding that the patient had negative manual direct antiglobulin test (DAT) by anti-C3d. It could be shown only by automated IAT that patient's serum also contained IgM cold agglutinins which also reacted best at 22 degrees C and appeared to be of lambda light-chain type. The patient responded to corticosteroid therapy and remains well without treatment 14 months after the hemolytic episode. The presence of IgG cold agglutinins may be predictive of a favorable response to corticosteroid therapy.

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.

Erythrocyte sensitization with monomeric IgM in a patient with hemolytic anemia

An automated antiglobulin test showed that erythrocytes of a patient with an acute episode of Coombs-negative hemolytic anemia were strongly sensitized with nonagglutinating IgM molecules. The bound antibodies, after elution from red blood cell stroma, were found to be monomeric IgM, since they migrated with IgG molecules on an agarose column, although they were proved to be immunoglobulin M, not G, by a sensitive hemagglutination inhibition assay. The hemolysis subsided with steroid therapy, but ANA increased to a titer greater than 1,024 (with peripheral pattern) without other laboratory evidence of systemic lupus erythematosus. In addition, the patient demonstrated photosensitivity and nonscarring alopecia. We consider that this appearance of erythrocyte autoantibodies consisting of monomeric IgM was a symptom of atypical SLE.

The significance of complement in immunohematology

In vitro detection of red cell-bound complement can be important in the differential diagnosis of autoimmune and drug-induced immune hemolytic anemias; it can also be a sensitive test for the detection of complement-binding alloantibodies, e.g., in compatibility testing. Red cell-bound complement can be detected by the antiglobulin test if suitable antiglobulin sera (AGS) are utilized. In 1971, the Federal Standards for AGS were criticized because so-called broad spectrum AGS used routinely in blood banks were shown to often be deficient in anticomplement reactivity. In the new few years commercial regents changed with regard to the quantity and specificity of their anticomplement components. A great deal of controversy developed as to the true importance of detecting red cell-bound complement, the particular fragments of complement that should be detected, and the causes of nonspecific reactions that seemed to be occurring, especially with the increasing usage of new techniques utilizing low ionic strength media. When monospecific anti-IgG and anti-C3 became available commercially, the controversy regarding diagnostic testing was resolved as direct antiglobulin testing could be performed with these reagents rather than the broad spectrum reagents. Two main questions remained: how rare are alloantibodies that are only detectable by the anticomplement component of AGS? How clinically significant are such antibodies? The results of our 3-year study indicated that such antibodies (usually anti-Kidd) occurred with a incidence of 1/8000 sera tested. Some of these antibodies seemed capable of shortening the life span of transfused red cells, as determined by 51Cr survival studies; some showed negligible cell destruction. Severe transfusion reactions due to such antibodies would seem unlikely. Individual laboratories will have to balance the risk of missing some complement-dependent antibodies of possible clinical significance with the increased nonspecificity encountered in their own laboratory with AGS containing anticomplement.

Antibodies reactive with surface membranes of cellular elements in the blood

Autoreactive antibodies or immune complexes may accelerate clearance of mature erythrocytes, leukocytes, and platelets from the circulation in patients with rheumatologic and immunologic disorders. The most compelling evidence for immune injury to hematopoietic cells exists in patients with systemic lupus erythematosus and patients with Felty's syndrome and its variants. These disorders may also cause tissue inflammation, which in turn commonly results in underproduction of erythrocytes and development of thrombocytosis. However, recent evidence indicates that underproduction of hematopoietic cells may also result from immune injury to cellular elements in the bone marrow. In many laboratories, sensitive techniques are now clinically available for the detection of cell-associated immunoglobulin and complement. These assays have helped confirm the role of antibody in the pathogenesis of autoimmune hemolytic anemia and idiopathic thrombocytopenic purpura. However, recent data indicate that there is probably a continuum between the amount of immunoglobulin and complement found on normal cells and that found in a variety of disease states. In several of these disorders, additional evidence will be required to establish that the increase in cell-bound immunoglobulin leads to a decrease in the life-span of the cell. In order to provide significant help to the clinician managing an individual patient, these serologic tests must be capable of identifying the portion of the cell-associated protein actually involved in the destructive process. The availability of monoclonal reagents capable of identifying restricted regions on cell-bound immunoglobulin may help identify molecules bound specifically as antibody and may help identify the antigens involved in autoimmune disorders.

Complement and Ig uptake by erythrocytes in low ionic strength solutions

We studied the uptake of immunoglobulin (Ig) and complement from plasma by red blood cells (RBC) under low ionic strength (LIS) conditions using Rh-negative RBC and anti-Rh antibodies. The ionic strength of plasma/RBC mixtures was lowered by dialysis against 5% mannitol, pH 6.0. The studies revealed that bromelin-modified RBC failed to bind either Ig or complement in low ionic strength conditions, but that unmodified RBC bound the majority of anti-D. The bound anti-D (consisting of IgG1, IgG3, IgA, and IgM molecules) could be eluted into 0.9% NaCl yielding a higher recovery of antibody than that obtained by specific absorption-elution techniques. Although uptake of Ig by RBC was independent of complement activation, the subsequent elution of bound Ig into normal ionic strength solutions was not. Small amounts of Ig remained on EC43 and EC4, but not on RBC that did not become complement sensitized during low ionic strength exposure. These findings suggest that Ig remained attached to RBC via a complement-RBC bond.

Quantitation of red blood cell-bound C3d in normal subjects and random hospitalized patients

A sensitive radiolabelled anti-antiglobulin method was devised and applied to quantitating red blood cell-bound C3d (RBC-C3d) in samples from 174 normal blood donors. C3d was demonstrable on all RBC examined; 98% of values fell over a broad range, with the highest values being approximately 3.5 X the lowest values (equivalent to 50-160 molecules of C3d per cell). RBC-C3d did not correlate with sex or age (over 18-65 years); indirect evidence suggests that values for the paediatric age group will fall in the same normal range. Studies on samples obtained weekly for 10-12 weeks from six adult males and six adult females indicated stable levels of RBC-C3 for individual subjects; i.e. high normals, mid normals and low normals remained in their characteristic range levels over the period of observation. For comparison, RBC-C3d was measured in samples from 313 randomly selected hospitalized adult patients. 33% of the values were above the normal range; 8% were elevated to a level likely to have been detectable by a direct anti-C3d antiglobulin test. The great majority of elevated values occurred in patients not ordinarily considered to have autoimmune conditions. The results provide background for studies of the aetiology and significance of RBC-C3d in health and disease.

Complement components detected on normal red blood cells taken into EDTA and CPD

Normal red blood cells (RBC) from fresh EDTA and CPD blood and from stored CPD blood were examined for the presence of bound subcomponents of C3 and C4. By serologic agglutination tests, only C3d was detectable on the cells. Incubation in compatible fresh normal serum (FNS) at 37 degrees C appeared to increase the amount of 3Cd on the RBC. C3b was serologically detectable only on stored CPD cells and only after incubation in compatible FNS. No. C4 components were detected on the cell surfaces in agglutination tests. Using an indirect labeling technique, small, but significant, amounts of C3d and C4d were found on all three types of untreated cells. C3b was present on stored CPD cells only. The indirect labeling technique showed a significant increase in C3d and C4d on all cells following incubation i- compatible FNS, whereas bound C3b was significantly increased only with stored CPD cells. There was no increase in bound C4b following serum incubation. The average number of C3d molecules per cell on normal EDTA cells was 557 and average Ko was 3.6 x 10(7) l/mol.

The low ionic strength reaction of human blood: relationship between the binding of serum immunoglobulin and complement of red blood cells and surface charge of the cells

Using the sucrose haemolysis reaction of Hartmann & Jenkins (1966) as a basic model, the low ionic strength reaction (LISR) of human blood was studied to determine: (1) serum Ig uptake by RBC with saline elution and 125I-IgG uptake, and (2) complement fixation (CF) to RBC with lysis of PNH cells and C3H/C4 antiglobulin haemagglutination (AH) of normal cells. The saline eluates were found to contain IgG and IgM with traces of IgA; their pH optima for the uptake by RBC were 6.0 +/- 0.5, 5.5 +/- 0.5 and c 5.0 respectively. The ratio of bound IgG to IgM was linearly related to the uptake pH. Both C4 AH and lysis were found to be optimum at pH 6.0--7.5, whereas the maximum C3 AH was at pH 6.0 +/- 0.5. The LISR performed at a constant pH (6.1 +/- 0.1) showed that an increasing concentration of neuraminidase (VCN) used in pretreatment of RBC was associated with a decrease in both IgG uptake and CF activity. A maximum VCN effect reduced the Ig uptake to c 20% of normal and abolished almost all the CF activity. An impaired LISR to various degrees was also observed with RBC pretreated with ficin, papain, bromelin, trypsin or protamine, and RBC from two individuals of En(a-) type. Preincubation of serum at LIS with and without RBC resulted in respectively a 'complete' and partial consumption of C in the fluid phase. The latter was not enhanced or inhibited by the addition of VCN-treated RBC for preincubation. A hypothesis is proposed suggesting that in the LSR the Ig uptake by RBC is an electrostatic interaction of the oppositely charged RBC and Ig and the CF to RBC results from C activation by the cell-bound IgG and IgM. In addition, a pH-dependent inactivation of the cell-bound C3 in the LISR is demonstrated.

Studies on the preservation of red blood cells. Attachment of the third component of human complement to erythrocytes during storage at 4 degrees C

Utilizing an automated antiglobulin test, we have investigated the presence of the third and fourth components of human complement on normal red blood cells (RBCs). Only negligible amounts of the fourth component, C4, could be detected on either freshly collected or stored RBCs. The fragment C3d of the third component, C3, was detectable on both freshly collected and stored normal RBCs. A product derived from C3 and reacting with anti-C3c antibody was only barely detectable on freshly collected normal RBCs. During storage of blood at 4 degrees C, increasing quantities of this material were detected on the RBC membrane. Bromelin treatment rendered stored RBCs completely nonreactive with anit-C3c antibody, whereas only partial loss of reactivity was observed following incubation with heated plasma. In contrast, incubation of EC43 with heated plasma completely abolished their ability to react with anti-C3c antibody. We suggest that the presence of this C3 fragment on stored RBCs may contribute to the development of "preservation injury".

The advantage of a build-up anti-globulin technique for the detection of immunoglobulin on the red cells of rabbits infected with trypanosomes. A preliminary report

A build-up anti-globulin technique has been used to detect immunoglobulin on the red cells of rabbits infected with Trypanosoma brucei brucei S 42 and 427. The method, which is useful for the detection of immunoglobulin on sparsely coated red cells, involves treating the red cells of infected rabbits with antiglobulin followed by alternate globulin and antiglobulin layers until a lattice is built up which allows agglutination to occur. The red cells of five infected rabbits have been tested with anti-rabbit IgG,-IgM and broad spectrum anti-globulin reagents at intervals after infection and following the administration of Berenil, a drug which destroys trypanosomes. The positive anti-globulin reactions which developed following inoculation with trypanosomes were much reduced after giving Berenil. The tests became more strongly positive again in two rabbits after reinfection.

Anti-Holley (hy): characterization of another example

Anti-Hy, in a serum of a black man who had received multiple blood transfusions, was found to be a warm reactive and polyclonal IgG antibody which did not bind complement in vitro. 51Cr-labeled Hy-positive red blood cells in the patient showed a shortened "2-component" survival curve. Hy antigens were not detected on leukocytes, platelets, or in the serum of Hy-positive individuals.