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 GM1b-derived ganglioside, GD1c(NeuG c,NeuGc), was shown to be the predominant ganglioside in rat thymocyte s and T-cells. Upon the activation of the thymocytes, the amount of GD 1c(NeuGc,NeuGc) increases remarkably, and additionally a novel species of GD1b, GD1b(NeuGc,NeuGc), appears as the other major ganglioside (N ohara, et al. (1993) J. Biol. Chem. 268, 24997-25000). In the present study, monoclonal antibodies (MAbs) against these two gangliosides hav e been generated. The MAb AC1 established by immunizing mice with puri fied GD1c(NeuGc,NeuGc) reacted strongly with GD1c(NeuGc,NeuGc) and wea kly with GD1b(NeuGc,NeuGc) by enzyme-linked immunosorbent assay (ELISA ). The other MAb AB1 obtained by immunization with GD1b(NeuGc,NeuGc) s howed a strong binding activity to GD1b(NeuGc,NeuGc) and no reactivity to GD1c(NeuGc,NeuGc) by ELISA. Flow cytometry analyses using these MA bs have revealed that an AC1-positive subset exists in a portion of re sting CD4(+)CD8(-) thymocytes and CD4(+) splenic T-cells. When the thy mocytes were activated with 12-O-tetradecanoylpholbol-13-acetate (TPA) and calcium ionophore A23187, the proportion of AC1(+) cells increase d remarkably and were detected not only in CD4(+) cells but also in CD 8(+) cells. An increase in the proportion of AC1(+) cells was also see n in activated T-cells. In contrast, AB1-positive cells were only dete cted in activated thymocytes, not in resting thymocytes, or resting or activated T-cells. These results implicate GD1c(NeuGc,NeuGc) in the a ctivation of thymocytes as well as T-cells, whereas GD1b(NeuGc,NeuGc) appears to be specifically related to the activation of thymocytes.