Differential expression of alpha 2-6 sialylated polylactosamine structuresby human B and T cells

We found that human peripheral B and T cells differed in the surface expres sion of alpha 2-6 sialylated type 2 chain glycans, In contrast to B cells, T cells expressed only sialoglycans with repeated N-acetyllactosamine (Gal beta 1-4GlcNAc) disaccharides. This finding was based on the specificity of the monoclonal antibodies HB6, HB9 (CD24), HD66 (CDw76), FB21, and CRIS4 ( CDw76) with the alpha 2-6 sialylated model gangliosides IV(6)NeuAcnLc(4)Cer (2-6 SPG), VI(6)NeuAcnLc(6)Cer (2-6 SnHC), VIII(6)NeuAcnLc(8)Cer (2-6 SnOC ), and X(6)NeuAcnLc(10)Cer (2-6 SnDC), We found that, in addition to their common requirement of an alpha 2-6 bound terminal sialic acid for binding, the antibodies displayed preferences for the length of the carbohydrate bac kbones. Some of them bound mainly to 2-6 SPG with one N-acetyllactosamine ( LacNAc) unit (HB9, HD66); others preferentially to 2-6 SnHC and 2-6 SnOC, w ith two and three LacNAc units, respectively (HB6 and FB21); and one of the m exclusively to very polar alpha 2-6 sialylated type 2 chain antigens (CRI S4) such as to 2-6 SnOC and even more polar gangliosides with three and mor e LacNAc units. These specificities could be correlated with the cellular b inding of the antibodies as follows: whereas all antibodies bound to human CD19 positive peripheral B cells, their reactivity with CD3 positive T cell s was either nearly lacking (HD66, HB9), intermediate (about 65%: HB6, FB21 ) or strongly positive (CRIS4, 95%), Thus, the binding of the antibodies to 2-6 sialylated glycans with multiple lactosamine units appeared to determi ne their binding to T-cells.