LEISHMANIA-MAJOR PARASITES SHARE AN EPITOPE WITH THE MURINE CD3-T CELL-RECEPTOR COMPLEX

After immunization of BALB/c mice with a low molecular mass fraction ( FrD; less than or equal to 31 kDa) isolated from a soluble extract of Leishmania major promastigotes, a panel of monoclonal antibodies (mAb) was obtained. One of these antibodies (mAb 9C) recognized a cytosol-a ssociated antigen from L. major of approximately 21 kDa as shown by We stern blot and immunoprecipitation. In addition, mAb 9C reacted with s urface structures of murine splenic T cells and T cell clones. Reactiv ity was confined to murine cells, but was not strain restricted. Immun oprecipitation studies and surface-labeling experiments with CD4(+) T cell clones acid the T cell receptor (TCR)(-)CD3(-) T cell line TG40 t ransfected with V alpha/beta chains from human TCR and concomitant co- expression of murine CD3 suggested that mAb 9C binds to an epitope loc ated within the murine CD3-TCR complex. In addition, mAb 9C induced st rong T cell proliferation. We conclude that L. major parasites share a n epitope with the murine CD3-TCR complex which is functionally import ant for T cell activation.