Developmentally regulated expression of peanut agglutinin (PNA)-specific glycans on murine thymocytes

Abstract

Intrathymic maturation of T lymphocytes is characterized by variable expression of O-linked Galβ1,3GalNAc glycans reactive with peanut agglutinin (PNA) lectin. Recent studies on human thymocytes show that conversion from PNA+ to PNA- phenotype is correlated with increased expression of α2,3 O-linked sialyltransferase (ST), which sialylates Galβ1,3GalNAc glycans, masking their binding sites for PNA. Interestingly, α2,3 O-linked ST expression is highest within the regions of the thymus containing the most immature and most mature thymocyte subsets, suggesting that RNA-specific glycans are intermittently masked by sialylation during thymic selection processes. Here, we studied expression of PNA receptors on developing thymocytes in the murine system using thymocytes from both normal mice and transgenic mice that are genetically arrested at the early phases of T cell development. 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 thymus. In addition, our data demonstrate that a similar set of polypeptides is variably masked by sialylation throughout T cell development.