Gangliosides involved in activation of rat T lineage cells

Gangliosides have long been known to be involved in T-cell activation. In our previous studies, a unique GMlb-derived ganglioside, GD1c(NeuGc,NeuGc), was shown to be the predominant ganglioside in rat thymocytes and T-cells. Upon the activation of the thymocytes, the amount of GD1c(NeuGc,NeuGc) increases remarkably, and additionally a novel species of GD1b, GD1b(NeuGc,NeuGc), appears as the other major ganglioside (Nohara, et al. (1993) J. Biol. Chem. 268, 24997-25000). In the present study, monoclonal antibodies (MAbs) against these two gangliosides have been generated. The MAb AC1 established by immunizing mice with purified GD1c(NeuGc,NeuGc) reacted strongly with GD1c(NeuGc,NeuGc) and weakly with GD1b(NeuGc,NeuGc) by enzyme-linked immunosorbent assay (ELISA). The other MAb AB1 obtained by immunization with GD1b(NeuGc,NeuGc) showed a strong binding activity to GD1b(NeuGc,NeuGc) and no reactivity to GDlc(NeuGc,NeuGc) by ELISA. Flow cytometry analyses using these MAbs have revealed that an AC1-positive subset exists in a portion of resting CD4+CD8- thymocytes and CD4+ splenic T-cells. When the thymocytes were activated with 12-O-tetradecanoylpholbol-13-acetate (TPA) and calcium ionophore A23187, the proportion of AC1+ cells increased remarkably and were detected not only in CD4+ cells but also in CD8+ cells. An increase in the proportion of AC1+ cells was also seen in activated T-cells. In contrast, AB1-positive cells were only detected in activated thymocytes, not in resting thymocytes, or resting or activated T-cells. These results implicate GD1c(NeuGc,NeuGc) in the activation of thymocytes as well as T-cells, whereas GD1b(NeuGc,NeuGc) appears to be specifically related to the activation of thymocytes.