The 3G11+ antigen, a marker for murine CD4+ TH1 lymphocytes, is a ganglioside

Two monoclonal antibodies (mAbs), SM3G11 and SM6C10, can be used to discriminate between functionally distinct murine CD4+ T cell subsets. In this study we use high-performance thin-layer chromatography and immunostaining techniques to show that the 3G11 mAb reacts with two bands of a ganglioside fraction from murine spleen and thymus, and rat spleen. The 6C10 antibody shows no evidence of glycolipid reactivity. The 3G11+ bands have a mobility between those of the reference gangliosides GD1a and GD1b from human brain. The 3G11+ reactive bands were eluted in the disialyl fraction of rat spleen gangliosides using DEAE anion-exchange chromatography. Treatment of spleen gangliosides with endoglycoceramidase eliminates 3G11 antibody binding over time, indicating that the antigen contains a Glc beta 1-1'ceramide linkage, characteristic of a glycosphingolipid. Treatment of thymus or spleen gangliosides with sialidase eliminates binding of 3G11, thus indicating that the 3G11 epitope is dependent on the expression of one or more sialic acid residues. Immunostaining studies with a variety of reagents indicate that the 3G11+ gangliosides: (i) probably do not contain either the asialo-GM1 or the GM1 core structures; (ii) are not recognized by mAbs specific for the oligosaccharides of asialo-GM2, GM2, GD2 and GD3 gangliosides; and (iii) are also not recognized by antibodies or reagents that are specific for several structures representative of other major glycosphingolipid classes. Overall, these studies strongly suggest that the 3G11+ gangliosides have structures that have not been previously recognized in murine lymphoid tissue. Structures that could account for the known properties of the 3G11+ molecules are described. Finally, ways in which the selective expression of 3G11+ gangliosides might be linked to functionally distinct T-cell behaviours are discussed.