DEVELOPMENTALLY-REGULATED EXPRESSION OF PEANUT AGGLUTININ (PNA)-SPECIFIC GLYCANS ON MURINE THYMOCYTES

Intrathymic maturation of T lymphocytes is characterized by variable e xpression of O-linked Gal beta 1,3GalNAc glycans reactive with peanut agglutinin (PNA) lectin. Recent studies on human thymocytes show that conversion from PNA(+) to PNA(-) phenotype is correlated with increase d expression of alpha 2,3 O-linked sialyltransferase (ST), which sialy lates Gal beta 1,3GalNAc glycans, masking their binding sites for PNA. Interestingly, alpha 2,3 O-linked ST expression is highest within the regions of the thymus containing the most immature and most mature th ymocyte subsets, suggesting that RNA-specific glycans are intermittent ly masked by sialylation during thymic selection processes. Here, we s tudied expression of PNA receptors on developing thymocytes in the mur ine system using thymocytes from both normal mice and transgenic mice that are genetically arrested at the early phases of T cell developmen t. Our results confirm and extend recent findings in the human system by showing that murine T cells sequentially progress from PNA(lo) --> PNA(hi) --> PNA(lo) stages during their differentiation within the thy mus. In addition, our data demonstrate that a similar set of polypepti des is variably masked by sialylation throughout T cell development.