Relevance of sialoglycoconjugates in murine thymocytes during maturation and selection in the thymus.
ABSTRACT Differentiation of most T lymphocytes is characterized not only by the variable expression of CD4/CD8 coreceptor molecules and increased surface density of the T cell antigen receptor, but also by changes in the glycosylation pattern of cell surface glycolipids or glycoproteins. In this work we evaluated the changes in the sialylation pattern in thymus sections from normal and dexamethasone treated mice. We used sialic acid specific lectins, such as Sambucus nigra agglutinin (SNA, NeuAcalpha2,6-Gal specific) and Maackia amurensis agglutinin (MAA, NeuAcalpha2,3-Gal specific). Our results indicate that the sialylation pattern was modified during the maturation process of thymic cells. The immature CD4-CD8- and CD4+CD8+ cortical thymocytes were recognized by SNA, whereas the mature single positive (CD4+ or CD8+) medullary cells, preferentially bound MAA lectin. However, in the corticomedullary region we found not only SNA+ cells, but also MAA+ cells. In the thymus of dexamethasone treated mice, the clusters of thymocytes undergoing apoptosis in the cortex were characteristically stained by SNA. These results suggest that in the initial stages of the differentiation pathway, a great number of thymocytes express an alpha2,6 linked sialic acid on their surface and as they progress to more mature stages there is a change in the sialylation pattern to alpha2,3 linked sialic acids probably due to a regulated expression of different sialyltransferases, which could be modulated by the thymic microenvironment.
- Gastroenterology 01/2011; 140(5). · 12.82 Impact Factor
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ABSTRACT: Sialic acids are the terminal glycan structures of many glycoproteins and glycolipids, and they play a key role in many biological processes. Sialic acids can be classified according to their linkages to underlying glycans as α-2,3-, α-2,6-, and α-2,8 sialic acids. In this study, the expression level and distribution of α-2,6 linked sialic acid in the third and final larval, mature prepupa, and pupa stages of Galleria mellonella were investigated by SNA (Sambucus nigra agglutinin) lectin immunofluorescence and lectin blot analysis. The immunofluorescence analysis showed that levels of α-2,6 linked sialic acid were high in larval stages, especially the last larval stage, lower in mature prepupa and absent in pupa. The results of lectin blotting with SNA were consistent with immunofluorescence results. From these results, it could be inferred that the level of α-2,6 linked terminal sialic acid in insect tissues declines during development and aging.Invertebrate Reproduction & Development - INVERTEBR REPROD DEV. 01/2009; 53(1):45-52.
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ABSTRACT: During the intrathymic development, the fate of the thymocytes depends largely on variable expression of CD4/CD8 markers and T cell receptor protein expressions. In addition, changes of cell surface glycosylation status also affect the thymocyte maturation. In this study the glycosylation alterations in thymic tissues from 1, 9, 13 and 16 days old mice were evaluated by histochemical and lectin blotting techniques. With alcian blue (AB) at pH 5.7/periodic acid-Schiff (PAS) stainings, it was shown that thymic microenvironments contained carboxlylated and sulfated glycosaminoglycans (GAGs). Strong positivity to AB at pH 2.5, which specific for sialomucins, was seen in some medullary thymocytes. Similarly, it was shown that with Maackia amurensis agglutinin (MAL) medullary thymocytes, but not cortical ones, contained alpha(2 --> 3) linked sialic acid structures. On the other hand, while reaction with peanut agglutinin (PNA), which specific for core disaccharide galactose beta(1 --> 3) N-acetylgalactosamine, was only seen in cortical thymocytes, reaction with Galanthus nivalis agglutinin (GNA), which specific for terminal mannose residues, was seen in both cortex and medulla. However, Datura stramonium agglutinin (DSA), which recognizes galactose beta(1 --> 4) N-acetylglucosamine, was not only cell-specific, but it was bound some thymic vessels. With lectin blotting studies, five glycoprotein bands of molecular weights approximately 39, approximately 54, 100, approximately 110 and approximately 212 were found which reacted with MAL, PNA and DSA as well as GNA. These results suggest that glycosylation patterns of cell surface glycoconjugates are modified during thymocyte selection processes of postnatal days.Journal of Molecular Histology 08/2008; 39(4):417-26. · 1.98 Impact Factor