CONSTITUTIVELY HYPOSIALYLATED HUMAN T-LYMPHOCYTE CLONES IN THE TN-SYNDROME - BINDING CHARACTERISTICS OF PLANT AND ANIMAL LECTINS

Previously, beta 1,3-galactosyltransferase-deficient (Tn+) and normal (TF+) T-lymphocyte clones have been established from a patient sufferi ng from Tn-syndrome [Thurnher et al. (1992) Eur J Immunol 22: 1835-42] . Tn+ T lymphocytes express only Tn antigen (GalNAc alpha 1-O-R) while other O-glycan structures such as sialosyl-m (Neu5Ac alpha 2,6GalNAc alpha 1-O-R) or TF (Gal beta 1-3GalNAc alpha 1-O-R) antigens are absen t from these cells as shown by flow cytometry using specific mABs for TF and sialosyl-Tn antigen, respectively. Normal T lymphocytes express the TF antigen and derivatives thereof. The surface glycans of Tn+ an d TF+ cells were then analysed by flow cytometry using the following s ialic acid-binding lectins: Amaranthus caudatus (ACA), Maackia amurens is (MAA), Limax flavus (LFA), Sambucus nigra (SNA) and Triticum vulgar e (WGA). Equal and weak binding of MAA and SNA to both TF+ and Tn+ cel ls was found. WGA, LFA and ACA bound more strongly to TF+ cells than t o Tn+ cells. Binding of ACA to TF+ cells was enhanced after sialidase treatment. To investigate the possible biological consequences of hypo sialylation, binding of three sialic acid-dependent adhesion molecules to Tn+ and TF+ cells was estimated using radiolabelled Fc-chimeras of sialoadhesin (Sn), myelin-associated glycoprotein (MAG) and CD22. Equ al and strong binding of human CD22 to both TF+ and Tn+ cells was foun d. Whereas binding of Sn and MAG to TF+ cells was strong (100%), bindi ng to Tn+ cells amounted only to 33% (Sn) and 19% (MAG). These results indicate that the in vivo interactions of T lymphocytes in the Tn syn drome with CD22 are not likely to be affected, whereas adhesion mediat ed by Sn or MAG could be strongly reduced.