Surfaces of murine lymphocyte subsets differ in sialylation states and antigen distribution of a major N-linked penultimate saccharide structure

Rat liver β-galactoside α-2,6-sialyltransferase and Vibrio cholerae sialidase were used with cytidine-5′-monophospho-N-acetyl-[³H]neuraminic acid (CMP-[³H]NeuAc) to specifically probe the distribution and sialylation state of Galβ1-4GlcNAc residues on N-linked saccharides on the surfaces of murine lymphocytes. The relative extent of exogenous sialyltransferase-mediated sialylation (per cellular protein) was thymocytes > T-cells > T-cell lymphoma (EL-4) > B-cells > B-cell lymphoma (AKTB-lb) > splenocytes. Prior desialylation increased exogenous resialylation by 23.8-, 13.1-, 7.1-, 7.9-, 7.0-, and 5.3-fold for splenocytes, B-cells, T-cells, EL-4, AKTB-1b, and thymocytes, respectively. Though numerous glycoproteins were labeled, the majority of the Galβ1-4GlcN Ac residues were detected on a relatively small number of cell surface proteins, many of which are well-defined lymphocyte antigens. Galβ1-4GlcNAc residues on thymocytes were found to exist in an undersialylated state on T200 but not on other antigens (e.g., Thy-1). T200 was found to be fully sialylated on mature cells (i.e., hydrocortisone-resistant thymocytes and splenic T-cells), suggesting that its sialylation state is developmentally regulated. These studies indicate that the number, sialylation state, and polypeptide distribution of the penultimate structure, Galβ1-4GlcNAc, differ on N-linked saccharides on the surfaces of different lymphocyte populations.