[Genetic susceptibility to norovirus infection]

Norovirus (NoV) are the most common cause of acute gastroenteritidis in humans worldwide. They are transmitted through consumption of contaminated food, or mostly by direct person-to-person contact. However, susceptibility to NoV infection is variable. NoVs recognize carbohydrate ligand, including A, B, H and Lewis histoblood group antigen (HBGAs) for attachment to human epithelial cells. Synthesis of these HBGAs requires various glycosyltransferase encoded by the ABO, FUT2, FUT3 genes. The presence of distinct carbohydrates structures dependent upon the combined polymorphism at the FUT2, FUT3 and ABO loci influences susceptibility to NoV infection. NoV-glycan interactions studies show that different strains recognize specific HBGAs. Together with herd immunity, HBGAs play a major role in the epidemiology and evolution of NoVs.

Infection by Helicobacter pylori expressing the BabA adhesin is influenced by the secretor phenotype

Helicobacter pylori (Hp) infects half the world's population and causes diverse gastric lesions, from gastritis to gastric cancer. Our aim was to evaluate the significance of secretor and Lewis status in infection and in vitro adherence by Hp expressing BabA adhesin. We enrolled 304 Hp-infected individuals from Northern Portugal. Gastric biopsies, blood and saliva were collected. Polymerase chain reaction (PCR) and immunofluorescence were used to detect BabA+ Hp in gastric biopsies. In vitro adherence by a BabA expressing Hp strain to gastric biopsies was performed. Secretor status was identified by Ulex, a lectin that recognizes secretor-dependent glycan structures in saliva and in gastric mucosa, and by Lewis(a/b) antibodies, and indirectly by identification of an inactivating mutation in the FUT2 gene (G428A). BabA status of infecting Hp was associated with CagA and VacAs1 (p < 0.05), intercellular localization of Hp (p < 0.01) and the presence of intestinal metaplasia (p < 0.05) and degenerative alterations (p < 0.005) in the biopsies. BabA was associated (p < 0.05) with Ulex staining of gastric biopsies and, although not significantly, to absence of homozygosity for FUT2 G428A inactivating polymorphism. In vitro Hp adherence was higher in cases wild-type or heterozygous for FUT2 G428A mutation (p < 0.0001), cases staining for Ulex (p < 0.0001) and a(-)b+ and a(-)b(-) secretor phenotypes (p < 0.001). In conclusion, BabA+ Hp infection/adhesion is secretor-dependent and associated with the severity of gastric lesions.

Fluorescent carbohydrate probes for cell lectins

Fluorescein labeled carbohydrate (Glyc) probes were synthesized as analytical tools for the study of cellular lectins, i.e. SiaLe(x)-PAA-flu, Sia2-PAA-flu, GlcNAc2-PAA-flu, LacNAc-PAA-flu and a number of similar ones, with PAA a soluble polyacrylamide carrier. The binding of SiaLe(x)-PAA-flu was assessed using CHO cells transfected with E-selectin, and the binding of Sia2-PAA-flu was assessed by COS cells transfected with siglec-9. In flow cytometry assays, the fluorescein probes demonstrated a specific binding to the lectin-transfected cells that was inhibited by unlabeled carbohydrate ligands. The intense binding of SiaLe(x)-PAA-3H to the E-selectin transfected cells and the lack of binding to both native and permeabilized control cells lead to the conclusion that the polyacrylamide carrier itself and the spacer arm connecting the carbohydrate moiety with PAA did not contribute anymore to the binding. Tumors were obtained from nude mice by injection of CHO E-selectin or mock transfected cells. The fluorescent SiaLe(x)-PAA-flu probe could bind to the tumor sections from E-selectin positive CHO cells, but not from the control ones. Thus, these probes can be used to reveal specifically the carbohydrate binding sites on cells in culture as well as cells in tissue sections. The use of the confocal spectral imaging technique with Glyc-PAA-flu probes offered the unique possibility to detect lectins in different cells, even when the level of lectin expression was rather low. The confocal mode of spectrum recording provided an analysis of the probe localization with 3D submicron resolution. The spectral analysis (as a constituent part of the confocal spectral imaging technique) enabled interfering signals of the probe and intrinsic cellular fluorescence to be accurately separated, the distribution of the probe to be revealed and its local concentration to be measured.

ABH and Lewis histo-blood group antigens, a model for the meaning of oligosaccharide diversity in the face of a changing world

Antigens of the ABH and Lewis histo-blood group family have been known for a long time. Yet their biological meaning is still largely obscure. Based on the available knowledge about the genes involved in their biosynthesis and about their tissue distribution in humans and other mammals, we discuss here the selective forces that may maintain or propagate these oligosaccharide antigens. The ABO, alpha 1,2fucosyltransferase and alpha 1,3fucosyltransferase enzyme families have been generated by gene duplications. Members of these families contribute to biosynthesis of the antigens through epistatic interactions. We suggest that the highly polymorphic genes of each family provide intraspecies diversity that allows coping with diverse and rapidly evolving pathogens. In contrast, the genes of low frequency polymorphism are expected to play roles at the cellular level, although they may be dispensable at the individual level. In addition, some members of these three gene families are expected to be functionally redundant and may either provide a reservoir for additional diversity in the future or become inactivated. We also discuss the role of the ABH and Lewis histo-blood group antigens in pathologies such as cancer and cardiovascular diseases, but argue that it is merely incidental and devoid of evolutionary impact.

Comparison of the three rat GDP-L-fucose:beta-D-galactoside 2-alpha-L-fucosyltransferases FTA, FTB and FTC

The complete coding sequences of three rat alpha1,2fucosyltransferase genes were obtained. Sequence analysis revealed that these genes, called FTA, FTB and FTC, were homologous to human FUT1, FUT2 and Sec1, respectively. A distance analysis between all alpha1,2fucosyltransferase sequences available showed that the two domains of the catalytic region evolved differently with little divergence between the FUT2 and Sec1 N-terminal domains, quite distant from that of FUT1. At variance, FUT1 and FUT2 C-terminal domains were less distant while a high evolutionary rate was noted for Sec1 C-terminal domain. Whereas FTA and FTB encode typical glycosyltransferases, FTC lacks the homologous start codon and encodes a protein devoid of intracellular and transmembrane domains. It is located on rat chromosome 1q34. Transfection experiments revealed that unlike FTA and FTB, FTC does not generate enzyme activity. Analysis by flow cytometry showed that H type 2 epitopes were synthesized in Chinese hamster ovary cells transfected by both FTA and FTB cDNA, but only FTB transfectants possessed H type 3 determinants. In REG rat carcinoma cells, both FTA and FTB allowed synthesis of H type 2 and H type 3 at the cell surface. Western blots showed that, in both cell types, FTA was able to synthesize H type 2 epitopes on a larger set of glycoproteins than FTB. Analysis of the kinetic parameters obtained using small oligosaccharides revealed only a slight preference of FTA for type 2 over other types of acceptor substrates, whereas FTB was barely able to fucosylate this substrate.

ABH and Lewis histo-blood group antigens in cancer

Antigens of the ABH and Lewis histo-blood group family can be found on many normal cells, mainly of epithelial type. In carcinomas, altered expression of the various carbohydrate epitopes of this family occur, and are often strongly associated with either a good or bad prognosis. A review of the available data on these tumor-associated markers, their biosynthesis and their prognostic value is proposed here. For a long time it has been unclear whether their presence could affect the behavior of carcinoma cells. Recent data, however, indicate that they play biological roles in the course of tumor progression. The presence of sialyl-Le(a) or sialyl-Le(x), which are ligands for selectins, promotes the metastatic process by facilitating interaction with the endothelium of distant organs. The loss of A and B antigens increases cellular motility, while the presence of H epitopes increases resistance to apoptosis by mechanisms that remain to be defined. The Le(y) antigen has procoagulant and angiogenic activities. All these observations are used to present a model that may account for the described associations between the presence or loss of these markers and the outcome of disease. Finally, their potential clinical applications as tumor-associated markers or as targets of immunotherapy are reviewed.

Binding of rabbit hemorrhagic disease virus to antigens of the ABH histo-blood group family

The ability of rabbit hemorrhagic disease virus to agglutinate human erythrocytes and to attach to rabbit epithelial cells of the upper respiratory and digestive tracts was shown to depend on the presence of ABH blood group antigens. Indeed, agglutination was inhibited by saliva from secretor individuals but not from nonsecretors, the latter being devoid of H antigen. In addition, erythrocytes of the rare Bombay phenotype, which completely lack ABH antigens, were not agglutinated. Native viral particles from extracts of infected rabbit liver as well as virus-like particles from the recombinant virus capsid protein specifically bound to synthetic A and H type 2 blood group oligosaccharides. Both types of particles could attach to adult rabbit epithelial cells of the upper respiratory and digestive tracts. This binding paralleled that of anti-H type 2 blood group reagents and was inhibited by the H type 2-specific lectin UEA-I and polyacrylamide-conjugated H type 2 trisaccharide. Young rabbit tissues were almost devoid of A and H type 2 antigens, and only very weak binding of virus particles could be obtained on these tissues.

Tk, a new colon tumor-associated antigen resulting from altered O-glycosylation

Erythrocyte polyagglutination antigens T and Tn are truncated O-glycan chains that are also carcinoma-associated antigens. We investigated whether Tk polyagglutination antigen could similarly be a carcinoma-associated marker and a target of immunotherapy. Monoclonal antibody LM389 was raised against Tk erythrocytes and tested by immunohistochemistry. LM389 strongly reacted with 48% human colorectal carcinomas. Labeling of normal tissues was visible on epithelial cells, mainly digestive, but was confined at a supranuclear level. Expression of the antigen on cloned human carcinoma cells correlated with sialosyl-Tn expression. O-Sialoglycoprotein endopeptidase treatment revealed that on carcinomas and cell lines, the epitope was present on O-glycans. Antibody specificity was determined using synthetic carbohydrates. Direct binding and inhibition studies indicated that LM389 best ligands were terminated by two branched N-acetylglucosamine units. Screening of murine cellular cell lines with LM389 allowed development of an experimental model with Tk-positive and -negative cells in syngeneic BDIX rats. Vaccination of rats with Tk erythrocytes provided a protection against growth of rat Tk-positive, but not of Tk-negative, tumor cells in association with the development of antibodies. Taken together, the results indicate that Tk polyagglutination antigen is a new colorectal carcinoma-associated antigen, absent from the normal cell surface, resulting from alteration of O-glycans biosynthesis and with potential as a target of immunotherapy.

Susceptibility of rat colon carcinoma cells to lymphokine activated killer-mediated cytotoxicity is decreased by alpha1,2-fucosylation

The presence of alpha1,2-fucosylated glycans at the surface of rat colon carcinoma cells has been associated with an increased tumorigenicity and resistance to natural killer/lymphokine activated killer (NK/LAK) cytotoxicity. We now report that transfection of rat alpha1,2-fucosyltransferases cDNA (FTA and FTB) into REG cells, which are spontaneously devoid of this enzymatic activity, allows expression of histo-blood group H antigen and increases their resistance to LAK, but not NK cell lysis. Conversely, transfection of PRO cells, which spontaneously express alpha1, 2-fucosyltransferase activity, with the FTA cDNA in the antisense orientation decreases expression of the H antigen together with their resistance to LAK cell lysis, but again, not to NK cell lysis. Furthermore, REG cells that are rejected by immunocompetent syngeneic rats are similarly rejected by rats depleted of NK cells by antibody 3.2.3, directed against the NKR-P1 molecule. Thus, the rejection of REG cells by immunocompetent rats and their earlier reported increased tumorigenicity after transfection with an alpha1, 2-fucosyltransferase cDNA cannot be ascribed to NK cell sensitivity or resistance, respectively. The increased resistance to LAK cell lysis, however, may be relevant to tumor progression.

alpha1,2Fucosyltransferase increases resistance to apoptosis of rat colon carcinoma cells

Accumulation of histo-blood group antigens such as Lewis b, Lewis Y and H in colon cancer is indicative of poor prognosis. It is accompanied by increase in alpha1,2fucosyl-transferase activity, a key enzyme for synthesis of these antigens. Using a model of colon carcinoma, we previously showed that alpha1,2fucosylation increases tumorigenicity. We now show that tumorigenicity inversely correlates with the cells' sensitivity to apoptosis. In addition, poorly tumorigenic REG cells independently transfected with three different alpha1,2fucosyltransferase cDNAs, the human FUT1, the rat FTA and FTB were more resistant than control cells to apoptosis induced in vitro by serum deprivation. Inversely, PRO cells, spontaneously tumorigenic in immunocompetent syngeneic animals and able to synthesize alpha1,2fucosylated glycans, became more sensitive to apoptosis after transfection with a fragment of the FTA cDNA in the antisense orientation. Expression of alpha1,2fucosyl-transferase in poorly tumorigenic REG cells dramatically enhanced their tumorigenicity in syngeneic rats. However, in immunodeficient animals, both control and alpha1,2fuco-syltransferase transfected REG cells were fully tumorigenic and metastatic, indicating that the presence of alpha1,2fucosylated antigens allowed REG tumor cells to escape immune control. Taken together, the results show that increased tumorigenicity mediated by alpha1,2fucosyl-ation is associated to increased resistance to apoptosis and to escape from immune control.

Role for alpha1,2-fucosyltransferase and histo-blood group antigen H type 2 in resistance of rat colon carcinoma cells to 5-fluorouracil

5-Fluorouracil (5-FU) is a drug of standard use in chemotherapy of colon carcinoma. However, its efficacy is limited by inherent and acquired cell resistance. Major changes in histo-blood group antigenic expression, at times associated with poor prognosis, occur on colon cancer cells. To assess whether these antigens might play a role in the resistance to 5-FU, a rat model of colon carcinoma was used. We observed that in vivo treatment of tumors with the drug increased expression of antigen H type 2. The increase was also observed after in vitro short-term exposure to 5-FU, as well as on a cell-resistant variant selected by continuous exposure to the drug, and was accompanied by an increase in alpha1,2-fucosyltransferase activity, the key enzyme involved in synthesis of H antigens. Transfection of cells devoid of this enzymatic activity by an alpha1, 2-fucosyltransferase cDNA allowed expression of H type 2 antigen and increased resistance to 5-FU. Inversely, transfection of cells which possess enzymatic activity by a cDNA in anti-sense orientation reduced both H type 2 cell-surface antigen and resistance to the drug. These results demonstrate that, in this experimental model, alpha1,2-fucosyltransferase and H type 2 antigen are involved in cellular resistance to 5-FU.

Glycosylation alterations of cells in late phase apoptosis from colon carcinomas

Comparisons of carbohydrate profiles between control and apoptotic colon carcinoma cells were performed by flow cytometry using a set of lectins and anti-carbohydrate antibodies. The six cell lines analyzed presented distinct carbohydrate profiles before induction of apoptosis. PHA-L and MAA binding decreased after induction of apoptosis by UV-treatment. In contrast an increase of PNA binding was observed after induction of apoptosis, except on SW-48 cells for which a decrease occurred. A decrease of SNA binding was observed after induction of apoptosis from strongly positive control cell lines, whereas it increased on weakly positive ones. All the blood group related antigens A, H, Lewis a, Lewis x, Lewis b, and Lewis y, had their expression strongly diminished on apoptotic cells. These changes occurred irrespective of the mode of apoptosis induction since similar results were obtained after UV, TNFalpha, or anti-Fas treatment. Fucosyltransferases activities were also decreased after apoptosis induction, except for alpha1,3fucosyltransferase in anti-Fas treated HT-29 cells, where it was strongly augmented. This could be attributed to the IFNgamma preteatment required to induce Fas expression on these cells. Fucosidase activity decreased after induction of apoptosis suggesting that it was not responsible for the loss of fucosylated structures. In the rat PRO cell line, H blood group antigens are mainly carried by a high molecular weight variant of CD44. It could be shown that the loss of H antigen after induction of apoptosis correlated with a loss of the carrier glycoprotein.

A rat experimental model for the design of vaccines against tumor associated antigens Tn and Sialyl-Tn

Clones either strongly or barely expressing the Tn and Sialyl-Tn antigens were isolated from a rat colon carcinoma cell line. Expression of the antigens in normal rat tissues was very restricted and vaccination using Ovine Submaxillary Mucin as the immunogen could delay growth of the Sialyl-Tn positive cells, but not of the Sialyl-Tn negative cells in syngeneic rats. The model should be useful for testing new anti-Tn or Sialyl-Tn vaccination protocols.

Increased tumorigenicity of rat colon carcinoma cells after alpha1,2-fucosyltransferase FTA anti-sense cDNA transfection

Accumulation of histo-blood group antigens such as Lewis b, Lewis Y and H increases tumor cell motility and tumorigenesis. Alpha1,2-fucosylation is a key step in the synthesis of these antigens. Two alpha1,2-fucosyltransferases, expressed in colorectal carcinomas, have been characterized (FUT1 and FUT2 in humans, FTA and FTB in rats). To define the relative contribution of each of these enzymes in tumor cell behavior, we have used an anti-sense transfection approach in rat colon carcinoma PROb cells, which synthesize mRNA encoding for both enzymes. We have previously reported that anti-sense transfection of a cDNA fragment of the FTB enzyme decreased H antigenic cell-surface levels and concomitantly decreased tumorigenicity. H antigens, detected by antibodies specific for H type 1, 3 or 4, were detected only on a splice variant of CD44 containing the product of exon v6. We now report the anti-sense transfection of an FTA cDNA fragment into PROb cells, which resulted in decreased enzymatic activity on a type 2 precursor and decreased cell-surface H type 2 antigen exclusively. Compared to controls, FTA anti-sense-transfected cells were significantly more tumorigenic in syngeneic animals but not in immunodeficient SCID mice. The UEA-I lectin, specific for H type 2, revealed that these structures were present on the CD44v6 variant and on an uncharacterized 80-kDa glycoprotein. Our results indicate that FTA and FTB fucosylate distinct glycan chains in the same cell, leading to opposite effects, under control of the immune system.

Carbohydrate-based probes for detection of cellular lectins

Carbohydrate (spacered saccharide residue, Glyc) probes with various tags were synthesized as analytical tools for study of cellular lectins, i.e., Glyc-polyacrylamide-3H, Glyc-PAA-biotin, Glyc-PAA-fluorescein (flu), and Glyc-PAA-digoxigenin, where PAA is a soluble polyacrylamide carrier of approximately 30 kDa. Binding of all types of probes, where Glyc is the sialyl Lewis X (SiaLeX) tetrasaccharide or a blank saccharide, was assessed using Chinese hamster ovary (CHO) cells either transfected with the E-selectin cDNA or mock-transfected. High binding of SiaLeX-PAA-3H to E-selectin-transfected cells and absence of binding to control cells (both native and permeabilized) allowed the conclusion that the polyacrylamide carrier and the spacer arm do not contribute significantly to the binding. The biotinylated probe showed a high level of nonspecific binding in cell enzyme-linked assays. A similarly built digoxigenin-labeled probe was significantly better. In flow cytometry assays, the fluorescein probe demonstrated a specific binding to E-selectin-transfected cells of a similar level to that given by an anti-E-selectin antibody. In addition, it could be inhibited by the anti-E-selectin antibody, further demonstrating specificity. Tumors were obtained from nude mice by injection of CHO E-selectin or mock-transfected cells. The fluorescent SiaLeX-PAA-flu probe could bind to tumor sections from E-selectin-positive CHO cells, but not from control CHO cells. These probes can thus be used to reveal specifically complex carbohydrate-binding sites on cells either in culture or on tissue sections.

Detection of a potential receptor for the H-blood-group antigen on rat colon-carcinoma cells and normal tissues

Up-regulation of the synthesis of carbohydrate tumor-associated antigens terminated by the disaccharide Fucalpha1-2Gal is frequent in colon carcinoma and associated with poor prognosis. There is evidence that Fucalpha1-2Gal (H-disaccharide) structures increase cancer-cell motility and tumorigenicity by as-yet unknown mechanisms. Using polyacrylamide-based neoglycoconjugates, we looked for a potential receptor for this disaccharide, and observed that a neoglycoconjugate probe containing the H-disaccharide could bind rat colon-carcinoma cells in a dose-dependent manner, whereas very little binding was evidenced when a probe containing glucose was used. Binding of the H-disaccharide probe could be inhibited by the free H-disaccharide as well as by unlabeled neoglycoconjugates containing a terminal H-disaccharide. The best inhibitor was the H-type-1 trisaccharide neoglycoconjugate. Histochemical detection of the potential H-receptor was performed on rat normal tissues and in situ 1,2-dimethylhydrazine-induced colon carcinomas. A strong binding of the H-disaccharide probe was evidenced on most tumors that could be partly inhibited by the trisaccharide Fucalpha1-2Galbeta1-4Glc and by the unlabeled H-disaccharide neoglycoconjugate, indicating carbohydrate specificity of the binding. Staining of normal colonic mucosa was much weaker. Strong staining was also observed on some normal tissues, such as the spleen or lymph nodes, while others, such as lungs or liver, were negative. Probes containing glucose or the Lewis-a trisaccharide did not stain tumors or normal tissues. These results provide preliminary evidence for the existence of H-specific binding sites, the number of which increases in colon carcinoma.

5-Fluorouracil-resistant colonic tumors are highly responsive to sodium butyrate/interleukin-2 bitherapy in rats

Advanced colorectal cancer is generally refractory to 5-fluorouracil (5-FU) chemotherapy. This is linked to the emergence of resistant cell populations, probably due to a selection process. The identification of molecular markers and the improvement of alternative therapies thus remain important. We have used as an experimental model a rat colon cancer cell line (PROb), which exhibits features similar to those of the human situation. 5-FU treatment of rats bearing PROb tumors enhanced their survival but did not lead to cure. A PROb 5-FU-resistant subline (PRObR1) was obtained by continuous in vitro exposure to 5-FU. Resistance to 5-FU was accompanied by a 2-fold increase in thymidylate synthase activity and a substantially higher incorporation of thymidine in the presence of 5-FU, compared with parental PROb cells. Unexpectedly, in syngeneic rats, PRObR1 tumors exhibited delayed growth when compared with parental PROb tumors. This was ascribed to an increased sensitivity of PRObR1 cells to host immune response since no growth delay was observed in immunocompromised nude mice and since there was no detectable difference in proliferation rates between PROb and PRObR1 cells. 5-FU treatment was inefficient in prolonging the survival of rats bearing PRObR1 tumors. In contrast, an immunotherapeutic protocol combining sodium butyrate and recombinant interleukin-2 (NaBut/rIL-2) cured 80% of the rats bearing established PRObR1 tumors. Our results suggest that NaBut/rIL-2 treatment is efficient against 5-FU-chemoresistant rat colon cancer.

Increase of rat colon carcinoma cells tumorigenicity by alpha(1-2) fucosyltransferase gene transfection

Fucosylated histo-blood group antigens such as Lewis b, Lewis Y, and H accumulate in colon carcinoma and this is accompanied by a clear increase in alpha(1-2)fucosyltransferase activity, a key enzyme for the biosynthesis of these antigens. Yet the biological significance of alpha(1-2) fucosylated structures is not well defined. We have transfected a poorly tumorigenic rat colon carcinoma cell line with the human H blood group alpha(1-2)fucosyltransferase cDNA. This resulted in cell surface expression of H antigens with a concomitant decrease of sialic acid substituted and free beta-galactosides. Immunoprecipitation experiments showed that H antigens were essentially borne by variants of CD44 carrying amino acid sequences encoded by exon v6. The transfected cells showed increased motility in a wound healing assay, without changing their proliferation rates. Parental and control cells transfected with an empty vector formed small tumors that always regressed after 30 days when injected subcutaneously to syngeneic rats. In contrast, alpha(1-2)fucosyltransferase transfectants were able to form progressive tumors. Increased tumorigenicity was also visible in nude mice. These results demonstrate that alpha(1-2)fucosylated antigens contribute directly to aggressiveness of colon carcinoma cells. This could occur by altering a function of CD44 variants.

Immunohistological analysis of antibodies against ABH and other glycoconjugates in normal human pyloric and duodenal mucosae

Eighty-eight monoclonal antibodies were tested by immunohistochemistry on human gastro-duodenal mucosae of known ABO, Lewis and Secretor phenotypes. Antibodies were classified among anti-A, anti-B, anti-AB, anti-H and other anti-glycoconjugates (I, i, T, Tn, Lewis, P1, Tk). Anti-A, B and AB antibodies were subdivided into subgroups with "broad" or "restricted" reactivity according to the extent of epithelial cell labeling. Anti-H antibodies were classified in accordance to their degree of sensitivity to the secretor phenotype. Among anti-T and anti-I antibodies, only one of each showed positive staining of epithelial cells. All anti-Lewis antibodies had distinct reactivities, although, they were clearly anti-Lewis reagents. Some anti-P1 antibodies labeled epithelial cells, irrespective of the ABO, Lewis and secretor phenotypes. One anti-Tk stained the Golgi apparatus of most epithelial cells, irrespective of the individual's phenotype. In conclusion, some of the antibodies tested were defined as very useful reagents for immunohistochemistry showing both specificity and sensitivity.

[Vaccination with genetically modified IL-2 secreting cells in a rat model of colonic carcinoma]

Genetically engineered tumor cells secreting immunostimulatory molecules could facilitate the obtention of a vaccination against tumor antigens. To test this approach, we transfected genes encoding for rat and mouse IL-2 into PROb cells. These cells originate from a dimethylhydrazine induced colon carcinoma of BD IX rats. We observed an inhibition of the in vivo tumor growth directly proportional to the IL-2 secretion. An immunohistochemical analysis revealed that the tumors were infiltrated by leucocytes expressing the IL-2 receptor, suggesting their activation within the tumor. A strong delay of tumor growth was observed in rats challenged with PROb cells after a previous rejection of IL-2 secreting cells. Yet two rats out of six were completely protected. This protection is specific since rejection of PROb-IL-2 does not confer protection towards the syngeneic glioma A15A5. In addition, we could show by depletion experiments that NK/LAK, CD8, and CD4 lymphocytes were involved in the rejection of cells secreting large amounts of IL-2. Macrophages appear to be involved in the rejection process too, but also in the induction of an immune memory. Vaccination experiments using irradiated PROb IL-2 cells were performed. Only a partial protection towards a challenge with parental PROb cells could be obtained, also depending on the amount of secreted IL-2: the best protection being obtained after vaccination with cells synthesizing a small amount of IL-2. However, this protection was not superior to that obtained by coinjection of irradiated PROb cells and BCG.

Immunization against a rat colon carcinoma by sodium butyrate-treated cells but not by interleukin 2-secreting cells

BACKGROUND & AIMS

Vaccination of patients with colon cancer with irradiated autologous tumor cells and bacille Calmette-Guérin (BCG) was reported to augment mean survival. It was recently observed that a local treatment combining recombinant interleukin 2 and the differentiation agent sodium butyrate cured rats with colon cancer peritoneal carcinomatosis. To optimize vaccination protocols, the comparison of the efficacy of irradiated tumor cells mixed with BCG with that of interleukin 2-gene-transfected cells and of tumor cells pretreated with sodium butyrate was performed.

METHODS

The poorly immunogenic rat colon carcinoma cells PROb were used in a vaccination assay. Interleukin 2-transfected PROb cells, either proliferating or irradiated, were used. The efficiency of irradiated PROb cells mixed with BCG, of interleukin 2-transfected cells, or of cells pretreated with sodium butyrate was tested.

RESULTS

Vaccination with irradiated parental cells and BCG did not provide protection. Irradiated interleukin 2-transfected cells were poorly efficient in the vaccination assay. Conversely, vaccination with irradiated parental cells pretreated with sodium butyrate before injection provided good protection.

CONCLUSIONS

Interleukin 2-secreting cells efficiently vaccinated animals when injected while replicating but not after irradiation. Conversely, sodium butyrate pretreatment provided a simple and efficient vaccination scheme that generated a long-term immune memory and allowed the use of irradiated cells.

Leukaemia Inhibitory Factor derived from rat colon carcinoma cells increases host susceptibility to tumour growth

We have tested Leukaemia Inhibitory Factor (LIF) production by 12 rat colon tumour clones isolated from a single cell line that display various degrees of tumorigenicity. A highly significantly relationship was found between levels of soluble LIF produced by the clones and their in vivo tumorigenicity. Such results suggested a role for LIF as a tumour facilitating agent. To test this hypothesis, the highly tumorigenic and LIF producing PROb clone was transfected with the LIF cDNA in antisense orientation in order to decrease LIF production. Conversely, REGb, a low LIF producer that is rejected by syngeneic animals, as well as nude mice, was transfected with the LIF cDNA to increase its production. PROb cells transfected with antisense cDNA were shown to have decreased LIF production along with decreased tumorigenicity. LIF-transfected REGb cells expressing high LIF levels still regressed in syngeneic rats, but could form progressive tumours in nude mice. We did not detect LIF receptors on PROb or REGb cells and their in vitro proliferation was not modified by the addition of exogenous LIF. Therefore, LIF was not an autocrine growth regulator for PROb and REGb cells. Instead, LIF appears to facilitate in vivo tumour growth, without being an immunosuppressive factor sufficient on its own to allow growth of immunogenic cells in fully immunocompetent hosts.

Co-segregation of tumor immunogenicity with expression of inducible but not constitutive hsp70 in rat colon carcinomas

Recent results have shown the importance of heat-shock proteins (hsp) in immune reactions. In addition, immunization against hsp purified from some immunogenic tumors specifically protects animals from a challenge with the tumor from which the hsp were purified. The protection is dependent on the association between hsp and immunogenic peptides. Using a model of rat colon carcinoma, we studied the importance of hsp70 expression in determining the tumorigenicity of cancer cells in immunocompetent syngeneic animals. Various clones with distinct tumorigenic potentials have been derived from the same parental tumor. Some clones are tumorigenic and others are rejected through an immune-based mechanism. It was observed that among all parameters tested, immunogenicity of tumors co-segregated with expression of inducible hsp70 but not with constitutive hsc70. Variants were obtained from a highly tumorigenic clone (PROb) and from a regressive clone (REGb). The PROb variant (Ph8), selected by repeated sublethal heat shocks, showed an increased capacity for hsp70 synthesis concomitant with a decreased tumorigenicity. Inversely, the REGb variant (REGR73), selected after in vivo growth in partially immunosuppressed rats, acquired tumorigenicity and lost the ability to synthesize hsp70. Expression of other immunologic mediators such as intercellular adhesion molecule-1, MHC I, and MHC II did not co-segregate with tumor immunogenicity. Depletion experiments showed that the immunity elicited by these tumors involves TCR-alpha beta-bearing T cells. Such observations imply that, in this experimental model, inducible but not constitutive hsp70 is involved in immunogenicity of tumors.

Co-segregation of tumor immunogenicity with expression of inducible but not constitutive hsp70 in rat colon carcinomas

Recent results have shown the importance of heat-shock proteins (hsp) in immune reactions. In addition, immunization against hsp purified from some immunogenic tumors specifically protects animals from a challenge with the tumor from which the hsp were purified. The protection is dependent on the association between hsp and immunogenic peptides. Using a model of rat colon carcinoma, we studied the importance of hsp70 expression in determining the tumorigenicity of cancer cells in immunocompetent syngeneic animals. Various clones with distinct tumorigenic potentials have been derived from the same parental tumor. Some clones are tumorigenic and others are rejected through an immune-based mechanism. It was observed that among all parameters tested, immunogenicity of tumors co-segregated with expression of inducible hsp70 but not with constitutive hsc70. Variants were obtained from a highly tumorigenic clone (PROb) and from a regressive clone (REGb). The PROb variant (Ph8), selected by repeated sublethal heat shocks, showed an increased capacity for hsp70 synthesis concomitant with a decreased tumorigenicity. Inversely, the REGb variant (REGR73), selected after in vivo growth in partially immunosuppressed rats, acquired tumorigenicity and lost the ability to synthesize hsp70. Expression of other immunologic mediators such as intercellular adhesion molecule-1, MHC I, and MHC II did not co-segregate with tumor immunogenicity. Depletion experiments showed that the immunity elicited by these tumors involves TCR-alpha beta-bearing T cells. Such observations imply that, in this experimental model, inducible but not constitutive hsp70 is involved in immunogenicity of tumors.

[Identification of spermatozoa L-selectin and two potential pellucida ligands]

At the molecular level, gamete interactions partly depend on zona pellucida-glycoproteins fucosylation. We show, by immunocytochemistry, the sialyl-lewisx and sialyl-lewisa oligosaccharides on human zonae pellucidae. These epitopes are potential ligands of cell adhesion molecules named selectins which are known to play a role in endothelium-leukocyte interactions. By immunofluorescence, we find the leukocyte selectin (L-selectin) on the spermatozoa head. Preincubation of spermatozoa with an anti-L-selectin monoclonal antibody produces a significant inhibition of zona pellucida tight binding, under hemizona assay conditions. In contrast, preincubation of the zonae pellucidae with anti-sialyl-lewisx or anti-sialyl-lewisa antibodies does not produce a significant inhibition of spermatozoa binding. Western blot analysis of spermatozoa-detergent extracts revealed a band at approximatively 90 kDa with the anti-L-selectin monoclonal antibody. This spermatozoa selectin could play a role in human spermatozoa-zona pellucida binding. Zona-ligands have yet to be precisely defined.

The expression of carbohydrate blood group antigens correlates with heat resistance

Recent data indicate that cells may resist heat shock via more than one route: heat shock protein synthesis and other still ill-defined mechanisms. We investigated this phenomenon using four types of cells derived from a single rat colon carcinoma: clones REGb and PROb; PRO A+, a glycosylation variant of PROb selected for its high expression of blood group A antigen; and Ph8, a thermoresistant variant of PROb selected by repeated sublethal heat treatments. Basal heat resistance was clearly associated with the level of cell surface expression of blood group H and A antigens. Biosynthesis of these carbohydrate structures requires two glycosyltransferases, H and A enzymes, whose activities are also correlated with basal heat resistance. In addition, heat sensitive REGb cells were rendered more resistant by transfection with the gene encoding for H enzyme, allowing expression of H antigen. Thus, these terminal glycosylations could play a role as cellular protectors against heat treatment. Blood group carbohydrate antigens were mainly located on O-linked carbohydrate chains of a major glycoprotein of 200 kDa and to a lesser extent on N-linked chains. Only trace amounts were present as glycolipids.

An interleukin 2/sodium butyrate combination as immunotherapy for rat colon cancer peritoneal carcinomatosis

BACKGROUND/AIMS

Immunotherapy using interleukin 2 has had disappointing results in the treatment of colon cancer. Overcoming escape mechanisms, such as lack of antigen presentation and absence of accessory adhesion molecules on cancer cells, may increase its efficiency. We tried to do so by modifying the phenotype of the weakly immunogenic rat colon cancer PROb cells with sodium butyrate.

METHODS

After in vitro treatment with butyrate, PROb cells were tested for lymphokine-activated killer cell sensitivity and, using cytofluorometry, expression of adhesion molecules. We then treated established PROb peritoneal carcinomatoses with intraperitoneal injections of interleukin 2 and butyrate. Tumors were studied histologically and immunohistochemically. We tested the specificity of the immune protection by subsequent subcutaneous challenges with either PROb or glioma cells and by Winn's assay.

RESULTS

Butyrate increased lymphokine-activated killer cell sensitivity and expression of major histocompatibility complex class I and intercellular adhesion molecule 1 in vitro. Interleukin 2/butyrate combination resulted in cases of complete cure of carcinomatosis with specific protection against PROb cells. We noticed a complex stroma reaction with numerous functional antigen presenting cells close to PROb cells.

CONCLUSIONS

The complete regression of tumor masses may be attributed, at least in part, to a butyrate-induced increase in immunogenicity of the cancer cells. This new combined immunotherapy may be of interest in the treatment of colon cancer.

H blood group antigen carried by CD44V modulates tumorigenicity of rat colon carcinoma cells

Expression of carbohydrate ABH blood group antigens is oncodevelopmentally regulated and their presence on tumor cells constitutes a prognostic factor. However, it is not clear whether they directly affect tumor behavior. Using a rat model of colon carcinoma, we previously observed an association between the presence of H blood group antigens and tumorigenicity in syngeneic animals. In the present study, we show by immunoprecipitation experiments that cell surface H blood group antigens of a highly tumorigenic clone (PROb) are essentially carried by splice variants of the CD44 molecule containing exon V6. PROb cells were then transfected with an antisense fragment of the gene coding for a rat alpha (1-2)fucosyltransferase. This enzyme allows synthesis of H antigens from various beta-galactoside precursors. Transfected subclones of PROb cells were obtained which had significantly decreased enzymatic activity and H antigenic cell surface levels. In contrast, no such changes were observed in control cells transfected with either the empty vector or with a sense fragment of the gene. Compared to controls, the antisense-transfected cells were far less tumorigenic in syngeneic animals. These results show that H blood group antigens at the surface of PROb colon carcinoma cells contribute to tumor progression. The presence of the fucosylated structures on CD44 could modulate the functions of this adhesion molecule.

A fucose-containing epitope potentially involved in gamete interaction on the human zona pellucida

The oligosaccharide moiety of human, porcine and bovine zonae pellucidae was studied with lectins and monoclonal antibodies specific for tri- or tetra-saccharidic epitopes containing at least one terminal alpha-L-fucose. Animal eggs were collected from follicular aspirates, human eggs were collected from in-vitro fertilization and embryo transfer programmes and pooled into six groups. By direct immunofluorescence, the lectins reactivity was detected for the animal or the human zonae pools in the same way. Reactivity of Aleuria aurantia lectin demonstrated the presence of alpha-L-fucose terminal residues in the zonae from the three species studied. By indirect immunofluorescence, the 2-25 antibody reactivity was detected in every pool of human zonae whereas there was no evidence of any antibody reactivity on animal zonae. Using an anti-Lewis-b blood group antibody (2-25), we observed expression of this antigen as an intrinsic component of the human zona pellucida, independently of patients' Lewis red blood cell phenotypes. Antibody 2-25 inhibited the spermatozoa-zona binding in a hemizona assay, suggesting that this fucose-containing antigen could be part of a sperm-zona receptor.

Expression of the 100-kda glucose-regulated protein (GRP100/endoplasmin) is associated with tumorigenicity in a model of rat colon adenocarcinoma

Resistance to glucose starvation and expression of glucose-regulated proteins (grp) were studied in a model of rat colon carcinoma. In this model, various clones originating from the same parental tumor showed distinct tumorigenic potential in syngeneic hosts. Some clones were tumorigenic while others were rejected by an immune-based mechanism. It appeared that the more tumorigenic clones were more resistant to glucose starvation and able to synthesize larger amounts of grp100 than non-tumorigenic clones in response to either glucose starvation or tunicamycin treatment. In contrast, there was no difference in the induced levels of synthesis of grp78 between tumorigenic and non-tumorigenic clones. These results suggest that the ability of cells to synthesize large amounts of the stress protein grp100 might allow them to resist marginal conditions imposed by fully immunocompetent hosts, thus conferring greater tumorigenicity.

Failure of monoclonal antibodies against tumor associated antigens to improve tumor targeting of LAK cells in a model of rat colon carcinoma

The possibility of targeting LAK cells to the tumor by arming them with monoclonal antibodies directed against tumor associated antigens was tested in a rat model of colon carcinoma. Peritoneal carcinomatosis was generated by injection of cloned tumor cells and 111In-labeled LAK cells were injected in the tail vein after preincubation with the monoclonal antibodies themselves. It appeared that the antibodies did not significantly improve tumor targeting of LAK cells, most of the radioactivity being recovered in the spleen, the liver, the kidney or the lung, and only a small fraction in the tumor.

Analysis of the relationship between stage of differentiation and NK/LAK susceptibility of colon carcinoma cells

NK and LAK cells which are able to lyse tumor target cells in an MHC-unrestricted manner are not equally effective against targets of the same nature. In the case of colorectal tumors, some cells are highly sensitive, whereas others are resistant to NK and can even be quite resistant to LAK-mediated lysis. In the present paper, we tried to correlate the stage of differentiation of 17 human colorectal tumor cell lines with their NK- or LAK-cell susceptibility. It was observed that NK cells killed colorectal target cells independently from their stage of differentiation defined according to histopathological criteria from xenografting in nude mice. NK susceptibility was not correlated either with in vitro-defined criteria of differentiation, such as cell polarity and morphology, brush-border enzyme expression and CEA production. A LAK-resistant HT-29 sub-line (HT-29 LAK) was selected which could not be distinguished from HT-29 in terms of features of differentiation. It was further observed that HT-29 Glc-/+ cell line, a highly differentiated enterocytic-like variant of HT-29, obtained after glucose starvation, was killed by LAK cells as efficiently as the moderately differentiated parental HT-29, and that Caco-2 cells, which differentiate spontaneously after confluence in standard culture conditions, were equally sensitive to NK-mediated lysis whatever their stage of differentiation. In contrast, HT29 MTX10(-5), a highly differentiated mucus-secreting variant of HT29 obtained by methotrexate selection, was much more resistant to LAK cells than parental HT29 cells.

Analysis of factors associated with the tumorigenic potential of 12 tumor clones derived from a single rat colon adenocarcinoma

We analyzed several factors which could influence the immunogenicity of colon tumor cells, using a series of clones derived from a single chemically induced rat adenocarcinoma cell line. These clones display variable tumorigenic potential in syngeneic immunocompetent animals, and it has been established that in this model the tumorigenicity of the cells depends on their ability to escape immune surveillance. The results show an absence of relationship between tumorigenicity and expression of MHC-class-I antigens, cell adhesion to rat fibroblasts or fibroblast extracellular matrix. The secretion of latent and active TGF beta I appeared to be quite variable from one clone to the other, but was unrelated to tumorigenicity. Unexpectedly, some regressive clones produced elevated levels of this cytokine, suggesting that in this model, spontaneous secretion of TGF beta I is not sufficient to impair the immune system of the host. In contrast, the more tumorigenic clones were more resistant than less tumorigenic ones to cytotoxicity mediated by NK or LAK cells. They also showed arrest of cell proliferation after reaching confluence, something not observed in the less tumorigenic clones. Finally, the strongest relationship with tumorigenicity was found for expression of blood-group carbohydrate antigens. Increased expression of blood-group-H antigen and, conversely, decreased expression of beta-galactoside precursors of this antigen correlated with increased tumorigenicity.

Involvement of histo-blood-group antigens in the susceptibility of colon carcinoma cells to natural killer-mediated cytotoxicity

The susceptibility to natural-killer-cell lysis and expression of histo-blood-group antigens of 2 clones from a rat colon adenocarcinoma, of variants derived from them and of 17 human colon carcinoma cell lines were assessed in an attempt to determine if the major glycosidic tissue antigens of epithelial cells could influence the NK susceptibility of tumor target cells of epithelial origin. The rat REGb clone, which is relatively NK-sensitive, expressed higher levels of precursor structures T and Tn and lower levels of H antigenic determinants than the PROb clone, which displays higher resistance to NK-cell lysis. Cell variants were obtained from these 2 clones; it appeared that whether the cell variants were selected on the basis of expression of a blood-group antigenic determinant or on the basis of altered susceptibility to NK-cell lysis, there was a link between increased resistance and higher expression of cell-surface A and H histo-blood-group antigens, or conversely, between increased sensitivity and higher expression of precursor structures. Similar conclusions were obtained upon study of the human cell lines, since a significant correlation was found between the level of expression of T or Tn antigens and sensitivity to NK-cell lysis. A significant relationship was found between the expression of Lewis antigens and increased resistance to NK-cell-mediated cytotoxicity.

Differential adhesion of rat colon carcinoma cells to fibronectin in relation to their tumorigenicity

We examined the fibronectin-adhesive properties of clones from a rat colonic cell line exhibiting distinct tumorigenicity in a syngeneic host. These cells were originally selected on the basis of differential adhesion to plastic surfaces. The TR cell line, when injected subcutaneously, forms a tumour which grows progressively and gives off metastases, whereas the TS cell line forms a small tumour which regresses within a few weeks. The regression is largely mediated by immunological factors and involves a fibroblastic reaction. REGb, a clone from the TS subline, adhered better to fibronectin or RGDS tetrapeptide than did PROb, a clone from the TR subline. However, there was little binding to the RGD tripeptide with either clone. The degree of adhesion was dependent on time and substrate concentration. After 6 h of incubation, 38% and 55% respectively of PROb and REGb cells bound to plates coated with 10 micrograms/ml fibronectin. Adhesion of both clones to fibronectin was inhibited to various degrees when cells were preincubated with RGDS, GRGDS or GRADSPK peptides, whereas other synthetic peptides such as RGD, GRGD or GRGFSPK were ineffective. Binding experiments using 125I-labelled fibronectin showed 39,000 fibronectin receptor sites on REGb cells but only 17,000 on PROb cells. Flow cytometry analysis using both anti-alpha 5 and anti-beta 1 integrins showed more fibronectin receptor sites on REGb than on PROb cells. Both approaches were in accordance with the higher adhesiveness of the REGb clone to fibronectin.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between sensitivity to natural killer cells and MHC class-I antigen expression in colon carcinoma cell lines

The sensitivity of colorectal tumors to NK-cell-mediated cytotoxicity and their expression of major histocompatibility complex (MHC) class-I antigens were studied in an attempt to determine whether such antigens play a role in the susceptibility of colorectal tumors to NK-cell lysis. In a rat colon-carcinoma model, 2 clones differing in their sensitivity to NK-cell-mediated cytotoxicity were tested for class-I expression; it was seen that the more sensitive cells (REGb) expressed less class-I products than did the resistant cells (PROb). However, when MHC class-I antigen expression was increased by IFN-gamma treatment, no change in NK-cell lysis was found with the PROb cells, while an increase in cytotoxicity was obtained with the REGb cells. After in vivo or in vitro selection of NK-resistant REGb cells, we observed in the selected cells an important decrease in RT-I class-I antigen expression. Fifteen different human colorectal cell lines were also studied for HLA class-I expression and NK-cell susceptibility, and no quantitative correlation between these 2 features was seen. However, cell lines which were deficient in HLA class-I antigens were more sensitive than class-I-positive cells.

Identification and characterization of a rat protein (p 105) auto-antigenic in rats bearing a progressive syngeneic colon carcinoma

Sera from BDIX rats inoculated with 2 tumor clones derived from a single syngeneic colon carcinoma were assayed by Western blotting for the presence of antibodies against the grafted tumor. The PROb clone is progressive and produces metastases. We observed that rats bearing this tumor developed antibodies against an unglycosylated water-soluble protein of 105 kDa. The magnitude of this humoral response, as assessed by the intensity of the signal on immunoblots, was inversely correlated with survival of the rats. Furthermore, rats inoculated with the REGb clone, which is immunologically rejected, never developed detectable antibodies against the tumor. Antisera from rats injected with PROb tumor detected p105 antigen in cellular extracts from the REGb clone and from a series of rat and human cell lines. This protein was also detected in variable amounts in some normal adult and fetal tissues. Treatment of PROb or REGb cells by either interferon-gamma or heat shock did not significantly alter the expression of the p105 auto-antigen.

The human chromosome 19 linkage group FUT1 (H), FUT2 (SE), LE, LU, PEPD, C3, APOC2, D19S7 and D19S9

Families segregating for deficiency of the H alpha-2-L-fucosyltransferase, FUT1, have been investigated for linkage between FUT1 and other markers on chromosome 19. The results provide evidence for close linkage between FUT1 and FUT2 and for looser linkage between FUT1 and APOC2 and between FUT1 and D19S7. Pairwise linkage data are also reported between other markers investigated.

Cellular expression of H and B antigens in the rat olfactory system during development

Developmental expression of H and B antigens in the rat olfactory system was studied from the embryonic day 14 up to the postnatal day 30. The H antigen was detected in the olfactory and vomeronasal epithelia as early as fetal day 14, whereas the B antigen first appeared 2 days later. The anti-H reagent reacted strongly with sensory receptors and weakly with supporting cells in both epithelia, whereas the anti-B reagent was specific for olfactory receptors. In the main olfactory epithelium, the H antigen was expressed from fetal day 19 by most of the receptor cells, whereas the B determinant was expressed from fetal day 16 to postnatal day 3 by only a few neuroreceptors mostly located near the epithelial surface. After the postnatal day 3, B positive neurons increased in number from the periphery toward the deeper mucosal layers and they were distributed over 3/4 of the epithelial thickness in 15- and 30-day-old rats. In the main olfactory bulb, a widespread glomerular B staining with variable binding intensity between adjacent glomeruli was already observed at birth. The vomeronasal receptor cells and their axon terminals in the accessory olfactory bulb exhibited a comparable developmental expression of the B antigen. Results suggest that the B antigen could be regarded as a marker of neuronal maturation of both the olfactory and vomeronasal receptor cells; moreover, its first appearance in the receptor cells might be temporally related to the formation of synapses between receptor axons and deutoneurons in the bulb.

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.

A hypothesis on the dual significance of ABH, Lewis and related antigens

ABH and related antigens appeared a long time ago in the evolution of vertebrates on tissues in contact with the external environment, which suggests that the polymorphism given by these antigens might play a role in the relationships of the species with pathogens. However, they are also oncodevelopmental markers and some recent experimental data suggest that they might play a role in cell-cell recognition at some stages of development. This type of function is difficult to reconcile with the polymorphic nature of these markers unless one considers that the glycosyltransferases necessary for the synthesis of the active structures are encoded by various members of multigene families. Some non-polymorphic members of the families would have their expression limited in time and space during development, leading to the same antigenic patterns in every individual, and these could reappear in some tumours, while the expression of other polymorphic members (A/B/O, H/h, Se/se, Le/le), leading to a variety of antigenic phenotypes, would be expressed at later stages and remain so during the whole life of the individual. The corresponding antigens could disappear from some cancer cells. It is argued that the ABH and related antigens would have primarily been involved in cell-cell recognition phenomena. The polymorphism would have evolved later from gene duplication under environmental pressure, the expression on erythrocytes which occurred very late in evolutionary time probably being of very little biological significance.

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.