R. Mollicone

Genetics of ABO, H, Lewis, X and related antigens

Abstract. The present knowledge on chemical, enzymatic, serologic and genetic aspects of ABH antigens is reviewed in an effort to produce a simple and coherent genetic model for the biosynthesis of these antigens and chemically related structures. The genetic control of type 1 (Lea, Leb, Lec and Led), type 2 (X, Y, I, and H), type 3 and type 4 ABH and related antigens in different animal and human tissues is analyzed, taking into account the properties of the glycosyltransferases which are involved in their synthesis and considering possible competition for common acceptor and donor substrates. The phylogeny of ABH determinants shows that they appeared as tissular antigens much earlier than as red cell antigens. The ontogeny of ABH antigens suggests that they behave as differentiation antigens, and an effort is made to correlate their tissular distribution in the adult with the embryological origin of each tissue.

Heterogeneity of the ABH antigenic determinants expressed in human pyloric and duodenal mucosae

We defined the chemical structure and the genetic control of the various A or B determinants expressed by pyloric and duodenal epithelial cells by indirect immunofluorescent staining using monoclonal anti-A or anti-B reagents that recognize only certain variants of A or B antigenic determinants.Some mucous cells in pyloric and Brünners glands express AY or BY antigens whereas other mucous cells in the same glands express only the Y antigen. Absorptive and goblet cells of the duodenal villi and Lieberkühn glands express mono- and difucosylated A or B structures, mainly of type 1. The pyloric surface epithelium expresses mono- and difucosylated, type 1 and type 2, A or B structures. In addition, A or B antigens, with a so far undefined structure are found in the pyloric surface mucosae of non-secretor individuals.

Heterogeneity of Anti‐A and Anti‐B Monoclonal Reagents

Abstract. Eight anti‐A and seven anti‐B monoclonal reagents were tested in parallel, with normal and weak ABH red cell phenotypes. A whole range of different reactivity patterns was found, but by making a comparison with the results obtained using polyclonal standard reagents, two major categories of reagents were distinguished: (a) stronger and more specific reagents, and (b) reagents similar to, or weaker than, the standard polyclonal controls. The analysis of the specificity of the reagents by tissue fluorescence staining and reactivity with synthetic oligosaccharides and purified glycolipids confirmed the existence of broad and restricted specificities. Two kinds of anti‐A1 reagents are described. One related to type 3/4 structures, which stains the Golgi apparatus, and another with broad anti‐A specificity which cross‐reacts with ‘A‐like’ structures. The inhibition of anti‐A reagents with salivas and synthetic oligosaccharide antigens gave parallel results for the secretor salivas and the difucosylated A antigens.

Red cell H-deficient, salivary ABH secretor phenotype of Reunion island. Genetic control of the expression of H antigen in the skin

Based on the genetic model proposing thatH andSe are two structural genes, we predicted that the red cell H-deficient, salivary ABH secretor phenotype should be found on Reunion island, where a large series of H-deficient non-secretor families have been previously described. Two such Reunion individuals are now reported. POU [Ah, Le(a−b+), secretor of A, H, Lea and Leb in saliva] and SOU [Oh, Le(a−b+), secretor of H, Lea and Leb in saliva]. Both are devoid of H α-2-fucosyltransferase activity in serum. In addition, the preparation of total non-acid glycosphingolipids from plasma and red cells of POU revealed the type 1ALeb heptaglycosylceramide and small amounts of the monofucosylated type 1 A hexaglycosylceramide. Both glycolipids possess an H structure probably synthesised by the product of theSe gene. No other blood group A glycolipids, with types 2, 3 or 4 chains, normally present in the presence of the product of theH gene, were found on red cells or plasma of POU.TheH,Se andLe genetic control of the expression of ABH and related antigens in different tissue structures of the skin is described in 54 H-normal individuals of known ABO, secretor and Lewis phenotypes; in one red cell H-deficient salivary secretor (SOU); and in one H-deficient non-secretor (FRA). Sweat glands express ABH under the control of theSe gene. Sweat ducts express ABH under the control of bothH andSe genes and Lewis antigens under the control ofLe and bothH andSe genes. Epidermis, vascular endothelium and red cells express ABH under the control of theH gene. The products ofH andSe genes are usually expressed in different cells. However, the results illustrate that in some structures, like the epithelial cells of sweat ducts, both the products ofH andSe genes can contribute to the synthesis of the same Leb structure.

Heterogeneity of Lewis Antibodies. A Comparison of the Reaction of Human and Animal Reagents with Synthetic Oligosaccharides

Abstract. Human as well as animal anti‐Lewis reagents were shown to have different binding patterns to synthetic structures chemically related to the Lewis epitopes. Two main types of cross‐reactions were found: (1) Cross‐reactions among type 1 Lewis epitopes (Lea, Leb and Lewis disaccharide). This type of cross‐reaction among different type 1 structures was predominant in anti‐Lea reagents (16 out of 18), although it was also present in some anti‐Leb reagents (4 out of 14). (2) Cross‐reactions of Lea and Leb with their type 2 isomers X and Y. The Leb‐Y cross‐reaction was more frequent (7 out of 14) than the Lea‐X cross‐reaction (2 out of 18). The serological property of some anti‐Lewis reagents reacting with cord cells (‘Lex’) is also shown to be heterogenous although probably related to common features of the type 1 Lea and Leb epitopes and independent of the type 2 X and Y epitopes.

Expression of ABH and X (Lex) antigens in various cells

Using a panel of reagents specific to the various subtypes of ABH antigens, it could be demonstrated that platelets carry ABH type 2 monofucosylated determinants on intrinsic glycoproteins. The presence of these antigens is controlled by the H gene and correlates with the presence of alpha-2-L-fucosyltransferase and the absence of alpha-3-L-fucosyltransferase. In contrast, intrinsic ABH antigens were not found on mononuclear cells, correlating with the absence of alpha-2-L-fucosyltransferase on these cells. However, after transformation with the Epstein-Barr virus and stimulation with 12-O-tetradecanoylphorbol-13-O-acetate (TPA), B lymphocytes were found to express the H antigen under control of the H gene and not the Se gene. The lymphoblastoid cell lines also expressed the X and sialylated X antigens which are normally markers of the myeloid lineage. These antigens are also normally found in epithelial cells of the digestive tract, kidney proximal convoluted tubules and hepatocytes. The alpha-3-L-fucosyltransferase responsible for the synthesis of this antigen is present in the serum but we report the existence of two individuals, a mother and her daughter, who lack more than 90% of this serum enzyme. The young girl suffers from a congenital kidney anomaly: oligomeganephronic hypoplasia. Her kidney tubules are devoid of X antigen. However, she and her mother have the X antigen on their granulocytes and its sialylated form on their monocytes. It therefore appears that there are distinct genetic controls for the expression of antigen X in different body compartments. This would be quite similar to the H and Se gene controls in tissues of distinct embryological origins.

On the Specificity of Human Anti‐H Antibodies

Abstract. Anti‐H antibodies from 2 homogeneous subgroups of H‐deficient individuals (Bombay and Réunion phenotypes) were studied for their specificity with regard to synthetic H oligosaccharides. It appears that Bombay individuals synthesize large amounts of both anti‐H type 2 and anti‐H type 1 antibodies, whereas Réunion individuals may possess strong anti‐H type 1 antibodies, but have only weak anti‐H type 2 antibodies in their serum. This can be explained by the presence of small amounts of H‐type 2 determinants on the erythrocytes of Réunion individuals contrasting with the complete lack of H determinants on the red cells of Bombay individuals.

Expression of ABH, Lewis and related tissue antigens in the human thymus.

Expression of ABH, Lewis and related antigens was studied in the thymus of children of known ABO, Lewis and secretor status using a panel of specific reagents. ABH and Lewis antigens partly under control of the secretor status were expressed on the Hassals bodies and a large fraction of the medullary epithelial cells. The sialyl‐Lea antigen was only present on some Hassals bodies of Lewis‐positive individuals. ABH but not Lewis antigens were also present on cortical epithelial cells but this was independent of the secretor status. The X, sialyl‐X and Y antigens were only expressed on Hassals bodies irrespective of the ABO, Lewis or secretor phenotype. Furthermore, the anti‐X and sialyl‐X antibodies labelled a subset of leucocytes of all the individuals tested. These results show that the genetic control of the expression of ABH and Lewis glycosidic tissue alloantigens in the thymus is different on cortical and medullary epithelial cells and stress the heterogeneity of the thymus epithelial cells.

Detection of Combined ABH and Lewis Glycosphingolipids in Sera of H‐Deficient Donors

Abstract. The sera of H‐normal, H‐weak and H‐deficient individuals transferred the same amounts of ABH and Lewis antigens to lymphocytes in culture, confirming that the circulating ABH and Lewis antigens detected by lymphocytotoxicity are independent of the H‐h system. These antigens were, as expected, under the control of the secretor and Lewis systems in the same way as exocrine secretions. These results suggest that both circulating ABH and Lewis glycosphingolipids and exocrine ABH and Lewis glycoproteins can be synthesized by the same tissues.