EA rosette formation: a simple means to increase sensitivity of the antiglobulin test in patients with anti red cell antibodies

The natural anti-alpha-galactosyl IgG in seminal fluid. A simple means to determine damage to the blood-genital tract barrier in infertile males

A simple method for detecting damage to the blood genital tract barrier (BGTB) is presented. The method is based on the ubiquitous presence of the natural anti-alpha-galactosyl (anti-Gal) IgG antibodies in high titers in the serum of every normal individual, and the interaction between this antibody and alpha-galactosyl residues on rabbit red blood cells (RabRBC). The binding of the anti-Gal antibodies to RabRBC could be demonstrated by the rosetting antiglobulin test. The seminal fluid (SF), normally compartmentalized from the blood, is devoid of anti-Gal reactivity. The SF of a large proportion of infertile males contained significant anti-Gal reactivity, implying transudation of serum IgG molecules probably due to damage in the selective permeability of the BGTB. The diagnostic potential of this assay is discussed.

Antiglobulin serum mediated phagocytosis of normal senescent and oxidized RBC: role of anti-IgM immunoglobulins in phagocytic recognition

Fresh human monocytes usually do not recognize normal RBCs; however, in our newly developed assay antiglobulin-opsonized normal RBCs were phagocytized. Both anti-IgG and anti-IgM fractions present in the antiglobulin serum were involved but the major opsonin was anti-IgM. The anti-IgM opsonized mainly senescent RBCs and therefore could be used to discriminate young from senescent RBCs. The antiglobulin serum and monospecific anti-IgM increased opsonization of in vitro oxidized and desialylated RBCs, whereas trypsin-treatment of RBCs decreased phagocytosis. The material removed by trypsin from the RBCs surface inhibited the antiglobulin and monospecific anti-IgM phagocytic assay supporting the view that membrane associated elements crossreacted with anti-IgM. These results suggest that both internal cellular events and external removal of sialic acid play a role in the emergence of non-IgG covered epitopes on the surface of senescent and oxidized erythrocytes.

Determination of ABO blood group zygosity by an antiglobulin rosetting technique and cell-based enzyme immunoassay

Two methods were employed to determine the zygosity of A and B red cells, the rosetting antiglobulin test and the enzyme-linked immunoadsorbent assay (ELISA) technique. By means of the rosetting antiglobulin test, clear differences between AA and AO as well as BB and BO could be shown; however, this method could not define the variation in the amount of the H antigen as a complimentary means of differentiating AA from AO and BB from BO. The ELISA test could quantitatively estimate the level of expression of H antigen, and using anti-A and anti-B reagents in a simultaneous assay, a specific pattern could be generated for each phenotype. Both rosette and ELISA approaches offer easy and inexpensive means of determining zygosity within the ABO system for use in paternity exclusion.

The natural anti-alpha-galactosyl IgG on human normal senescent red blood cells

A highly sensitive antiglobulin test based on rosette formation due to the interaction between IgG bearing red blood cells (RBC) and Fc receptors on K562 cells, was used to study the immunoglobulin molecules present on human senescent RBC. Normal human RBC were separated into young and senescent subpopulations on the basis of age-dependent differences in density by centrifugation on a discontinuous density Percoll gradient, and by flotation on phthalate ester mixtures. The senescent but not the young RBC were found to bear membrane bound IgG. Most of the bound IgG molecules could be specifically eluted by galactose in its alpha-anomeric form. Antigalactosyl (anti-Gal) IgG antibodies with similar reactivity were found to be present in high titres in every one of the 400 normal human sera tested. The natural anti-Gal antibodies isolated from normal sera by affinity chromatography could bind to IgG depleted senescent RBC but not to young RBC. Erythrophagocytosis experiments indicated that the anti-Gal bound to the senescent RBC induced their destruction by macrophages. It is suggested that the natural anti-Gal antibodies interact with cryptic alpha-galactosyl residues which are exposed in the course of the RBC senescence and mediate the removal of these RBC from circulation by cells of the reticuloendothelial system.

Excessive binding of natural anti-alpha-galactosyl immunoglobin G to sickle erythrocytes may contribute to extravascular cell destruction

A large proportion of sickle erythrocytes is removed from the circulation by the macrophages of the reticuloendothelial system. In view of the proposed role for natural antibodies in the destruction of normal senescent erythrocytes, we looked for a possible similarity in the antibodies that bind in situ to senescent and sickle cells. Bound IgG molecules were detected by a highly sensitive rosetting antiglobulin test, using K562 myeloid cells. After separation on Stractan density gradients, the 0.6% most dense (senescent) normal cells and the most dense 40% sickle cells displayed membrane-bound IgG as reflected by the high proportion of rosettes formed. No antibody was found on low-density cells of either type. The bound antibodies were readily eluted from both sickle and normal senescent cells by carbohydrates containing alpha-galactosyl residues. These antibodies appear identical to the recently discovered human natural anti-alpha-galactosyl IgG (anti-Gal), an IgG antibody present in high titers in normal sera. Moreover, affinity-purified anti-Gal interacted specifically with sickle and normal cells depleted of the autologous antibodies. A similar pattern of binding to the various erythrocyte subpopulations was observed when the radiolabeled lectin with anti-alpha-galactosyl specificity, Bandeiraea simplicifolia, was used. In vitro phagocytosis of normal and sickle erythrocyte subpopulations correlated with the presence of anti-Gal on these cells. The in situ binding of anti-Gal to a large proportion of sickle erythrocytes may reflect an accelerated physiologic aging process by which immune recognition of prematurely exposed alpha-galactosyl-bearing antigenic sites contributes to shortened cell survival.

Human natural anti-alpha-galactosyl IgG. II. The specific recognition of alpha (1----3)-linked galactose residues

A natural IgG antibody (anti-Gal) with alpha-galactosyl binding specificity has been found in large amounts (0.5 - 1.0% of serum IgG) in all individuals tested. It has been purified by affinity chromatography on a column of melibiose-Sepharose. In addition to its affinity for normal and pathological senescent human red cells, the antibody readily interacts with rabbit red blood cell (RRBC) glycolipids with alpha-galactosyl terminal residues. Two types (glycosidic linkages of 1----3 vs. 1----4) of rabbit red cells glycolipids with terminal alpha-galactosyl residues were tested for antibody binding. The antibody specifically bound to glycolipids with Gal alpha 1----3 terminal residues, and treatment of these glycolipids with alpha-galactosidase abolished binding. Hemagglutination inhibition studies with oligosaccharides of known structure also showed that the antibody binds specifically to glycoconjugates with an alpha 1----3 terminal galactose residue. Anti-Gal did not bind to a human B-active glycolipid, indicating that fucose-linked alpha 1----2 to the penultimate galactose prevents anti-Gal binding. The anti-Gal specificity for RRBC glycolipids also paralleled that of the alpha-galactosyl-specific Bandeiraea simplicifolia lectin. The possible reasons for the occurrence of this unique antibody in human serum are discussed.

The rosetting antiglobulin test as a means of determining the D zygosity of human red cells

The erythrocyte-antibody rosetting antiglobulin test was used to determine differences in the expression of various Rh antigens on homozygous and heterozygous Rh positive red blood cells. The rosetting antiglobulin test was able to detect the relative difference in expression of C, c, E and e on homo- and heterozygous red blood cells. Based on these findings, the test was used and found suitable for determining the genotypes of various D positive red blood cells.