Anti-Blood Group Lewis A Antibody [7LE] (A85793)

Cell surface carbohydrate structures including sialyl-Lewis X (sLe(x)) and Lewis Y (Le(y)) are important ligands in normal and malignant tissues. The aim here was to determine the possible influence on the expression of such antigens by two viruses varicella-zoster virus (VZV) and cytomegalovirus (CMV) involved in persistent infections of humans. We found that infection of human diploid fibroblasts with both viruses resulted in transcriptional activation of several fucosyltransferase (FUT) genes that were either dormant or expressed at low levels in uninfected cells. Both viruses induced FUT3, FUT5, and FUT6, encoding alpha1,3- and/or alpha1,4-specific fucosyltransferases. CMV, but not VZV, induced transcription of FUT1 (encoding an alpha1,2-specific fucosyltransferase), FUT7, and FUT9. The changes in transcription of FUT genes were expectedly associated with expression of Le(y) in CMV-infected cells and sLe(x) in the VZV-infected fibroblasts although no expression of these antigens was observed in uninfected cells. One major explanation for this difference between CMV- and VZV-infected cells was that CMV, but not VZV, induced expression of FUT1, necessary for Le(y) expression. The induced carbohydrate antigens in CMV- and VZV-infected cells could be of significance for virus spread and possible escape from immune responses.

Seven monoclonal antibodies (MAbs) reacting with high-molecular-mass components (greater than 20,000 kDa) isolated from an ovarian mucinous cyst of an A Le(a-b+) patient are described. By the use of immunoradiometric methods, these MAbs characterized seven different epitopes associated with components having a density of 1.45 g/ml by CsCl-density-gradient ultracentrifugation, like mucins. Two MAbs reacted with A and Lewis blood-group antigens respectively (polysaccharide epitopes). The five other MAbs characterized five M1 epitopes (called a, b, c, d and e), mainly associated with components of more than 20,000 kDa and 2000 kDa. They were completely destroyed by papain and 2-mercaptoethanol treatment (polypeptide epitopes). Moreover, timed trypsin digestion of native mucin resulted in a progressive loss of M1 activity and degraded these mucins into smaller M1-positive fragments. The a and c epitopes were partially degraded from relatively high-molecular-mass fragments (2000 kDa to 500 kDa) into a 100 kDa fragment. The b and d epitopes were completely degraded into smaller fragments ranging from 100 kDa to 40 kDa. The e epitope was completely destroyed by trypsin. These different pathways of M1 antigen degradation suggest the occurrence of different epitopes located in separate regions of the mucin molecules.

To explore the dynamics of the progressive loss of cell differentiation observed in the gastric precancerous process, the abnormal expression of Lea antigen in the gastric epithelium was investigated. Gastric biopsy specimens of 122 subjects with Le(a-b+) phenotype who had intestinal metaplasia of the gastric mucosa were studied. The subjects are residents of a rural area in the Colombian Andes with very high risk of gastric cancer. The abnormality was detected with increasing frequency in lesions with other markers of progression of the precancerous process, namely, colonic-type of morphology of the metaplastic cells, expression of sulfomucins, and dysplastic changes. The concomitant expression of the abnormal Lea antigen and sulfomucins was found to be a more reliable marker of more advanced lesions such as colonic metaplasia and dysplasia than either marker alone.

PURPOSE:

Mucin-related antigens are abundantly expressed by the cells of the normal human conjunctiva. The pattern of these antigens in pterygium, and especially the role of Galbeta1-3GlcNAc alpha2,3-sialyltransferase (ST3Gal III), sialyltransferase necessary to build the sialyl-Le(a) (Lewis(a)) antigen, were studied.

METHODS:

Immunoperoxidase staining was performed on 28 pterygia using different monoclonal antibodies: anti-M1 (against the peptidic core of gastric mucins encoded by MUC 5AC gene), anti-Le(a)(7LE), anti-sialyl Le(a)(NS 19-9), and anti-Le(b)(2-25LE). A serologic Lewis determination was done in 18 patients. ST3Gal III sialyltransferase expression was also studied in 10 healthy conjunctiva and 10 pterygia by reverse transcriptase-polymerase chain reaction (RT-PCR). Glyceraldehyde-3-phosphate-dehydrogenase was used as an endogenous internal control.

RESULTS:

First, Le(a), sialyl Le(a), and Le(b) immunoreactivities either decreased or were no longer detectable in pterygium goblet cells as opposed to normal conjunctiva. Second, unlike in pterygium, the Lewis immunoreactivity, which is mainly located in the surface epithelial cells in the normal conjunctiva, was occasionally restricted to the epithelial cells of the deep layers. However, M1 mucins did show an identical pattern expression in a normal conjunctiva and pterygium. ST3Gal III expression was significantly lower in pterygium (0.20+/-0.02 AU [arbitrary units]) than in normal conjunctiva (0.95+/-0.12 AU).

CONCLUSIONS:

ST3Gal III gene is less expressed in pterygium than in normal conjunctiva. This observation could explain the decrease of sialyl Le(a) expression observed in pterygium by immunohistology.