Significance of spontaneous autorosettes in rats

Rosetting of bovine T-lymphocytes with autologous and allogeneic red blood cells

Certain bovine peripheral blood lymphocytes (PBL) and foetal thymocytes were shown to bind autologous and allogeneic red blood cells (RBC). When autologous RBC were treated with dextran, approximately 10% of peripheral blood lymphocytes and about 30% of thymocytes were found to form rosettes. Cells forming autologous rosettes appear to be a population of T-lymphocytes because (1) more rosette formation occurred with thymocytes than with PBL, (2) autologous rosette formation was increased in PBL cultures enriched in T cells and was decreased in cultures depleted of T cells, (3) very few rosette forming cells had surface immunoglobulin and (4) peripheral blood mononuclear cell cultures depleted of monocytes did not show a decreased autologous rosette formation. It appears that the cells forming rosettes with autologous and allogeneic RBC belong to the same sub-population of T-cells.

In vivo ageing of rat erythrocytes and cell surface labeling by D-galactose oxidase and sodium borotritide

1. Young and old rat erythrocytes, separated in vitro, according to their age in vivo, were radioactively labeled at the cell surface D-galactosyl and 2-acetamido-2-deoxy-D-galactose (Gal and GalNAC) residues by treatment with D-galactose oxidase, followed by reduction with sodium borotritide: 2. The number of labeled surface residues per erythrocyte was found to be 0.52 X 10(6) +/- 0.08 X 10(6) for young, 0.38 X 10(6) +/- 0.05 X 10(6) for middle-aged and 0.32 X 10(6) +/- 0.05 X 10(6) for old, indicating a significant decrease of these surface Gal and GalNAC residues during ageing. 3. Qualitative changes were observed between the sodium dodecyl sulfate electrophoretic patterns of young, middle-aged and old labeled erythrocytes. 4. Quantitative changes were previously observed between the electrophoretic patterns of the labeled glycoproteins from young, middle-aged and old human labeled erythrocytes. 5. It is concluded that some of the changes occurring during in vivo ageing of rat and of human erythrocytes are different.

Anti-self receptors. I. Direct detection of H-2L region-restricted receptors on murine thymocytes

A high proportion (20--50%) of murine thymocytes form rosettes with either syngeneic or allogeneic erythrocytes. The specificity of this interaction was investigated by measuring the ability of different erythrocyte sonicates to inhibit rosette formation. With erythrocyte sonicates from recombinant mouse strains it was demonstrated that rosetting with syngeneic erythrocytes was mediated by H-2L and/or H-2D region-restricted receptors. The specificity of autorosetting was directly mapped to the H-2L region by the inability of erythrocyte sonicates from the BALB/c-H-2dm2 mutant, an H-2L-deletion mutant, to inhibit the rosetting of wild-type (BALB/c) thymocytes. The B10,2D2-H-2dm1 mutant, which has substantially modified H-2L and H-2D antigens, supported this conclusion. Furthermore, anti-H-2L sera were able to specifically block the inhibition of rosetting by erythrocyte sonicates. The above procedures clearly implicated the H-2L region in the thymocyte rosetting of d and k haplotypes. With the s haplotype the rosetting receptor was mapped to the H-2L/H-2D region, whereas with the b and q haplotypes rosetting was only mapped to the D end of the H-2 complex. This study also suggested complete cross-reaction between the thymocyte receptors carried by the k and d haplotypes, whereas the receptors of b, q, and s haplotypes were haplotype specific. In addition, the inhibition assay indicated that the rosetting of thymocytes with allogeneic and xenogeneic (rat) erythrocytes was mediated by a receptor primarily directed against self-H-2L. Finally, the critical role played by the H-2L region in this rosetting phenomenon was demonstrated by the inability of thymocytes from the H-2L-deletion mutant (H-2dm2) to rosette with syngeneic, allogeneic (rat) erythrocytes.

Age dependent reaction of mouse thymus cells with autologous and syngeneic erythrocytes

The age dependent events influencing the rosette forming capacity of Balb/c thymus and spleen cells against autologous or syngeneic erythrocytes were examined. A large number of autologous and syngeneic rosette forming cells (RFC) were observed in normal Balb/c mice in vitro. RFC were significantly greater in the thymus than in the spleen. The rosette forming T-cells (T-RFC) have the following characteristics: newborn Balb/c thymus has T-cells which react syngeneic erythrocytes from older donors. The T-RFC showed broad cross-reactivity with erythrocytes from other mouse strains but low reactivity with human or sheep erythrocytes. The auto and syngeneic T-RFC could be enhanced by non-specific serum proteins (FCS or BSA) or EDTA but was effectively inhibited by normal mouse serum. T-RFC resided in the cortisone sensitive population. The data indicate that the development of autologous and syngeneic rosette formation of thymus cells is dependent on the age of the erythrocyte donor. The age dependent change on the erythrocyte surface occurred relatively early in the life of the animal. The results also imply that certain subpopulations of thymus lymphocytes are capable of recognizing possible surface antigenic changes of the erythrocytes.

Autoagglutinin produced by organ fragment cultures of mouse spleen

Mouse spleen fragment microcultures produced a heat-labile substance which agglutinated syngeneic erythrocytes. The substance reacted with an antigen present on some strains of mouse erythrocytes and on rat erythrocytes, but absent from other strains of mouse erythrocytes and from guinea pig, rabbit or sheep erythrocytes. Agglutination was inhibited by antisera to mouse immunoglobulins except for antisera specific to mouse IgM which enhanced agglutination. The agglutinin sedimented with 19 S Ig on ultracentrifugation and was destroyed by pretreatment with mercaptoethanol. Using a rosette assay increased numbers of cells, specifically binding syngeneic erythrocytes by means of a surface Ig receptor were demonstrated in spleen fragment microcultures. It is considered that the agglutinin is a noncomplement-activating IgM autoantibody and that the precursors of the cells producing the autoantibody are detected by the rosette assay.

Human autologous and allogeneic rosettes

Human red blood cells can bind to human peripheral blood lymphocytes. The percentage of these rosette-forming cells (TEh) depends on various conditions including temperature and the use of selected foetal calf serum. It is improved by toluidine blue. Prior incubation at 37 degrees C is not necessary. ABO and rhesus antigen D have no influence on rosette formation. Analysis of human rosettes in T and B cell rich populations, in patients with chronic lymphatic leukaemia or T cell lymphoma provides further evidence that human autologous and allogeneic rosette-forming cells belong to a T cell subpopulation.

Changes in carbohydrate content of surface membranes of human erythrocytes during ageing

The carbohydrate content (neutral hexoses, fucose, sialic acid, and hexosamine) of human erythrocytes is significantly higher in young than in old erythrocytes. The differences observed in the carbohydrate content of surface glycopeptides, obtained after incubation with either Pronase or trypsin, is still more striking, suggesting important modifications of the carbohydrate moeties of the erythrocyte membrane during in vivo ageing.