Novel antigenic determinants of the T200 glycoprotein expressed preferentially by activated cytotoxic T lymphocytes.

This report describes the production and characterization of MAb specific for neoantigenic determinants, called CT antigens, present on the T200 glycoprotein of CTL. The CT determinants are expressed at high levels only on activated CTL. Although differences had previously been noted in the cell surface protein profile of distinct T cell subsets, this is the first description of a lineage-specific activation antigen. Furthermore, these determinants appear to have functional significance, because the CT-specific MAb block cytolytic function. Immune precipitation experiments indicated that the appearance of the CT antigens correlated with m.w. changes and the appearance of additional T200 protein species that were CTL specific. MLC cells cultured in the presence of IL 2-containing supernatants undergo a gradual shift from relatively low CT antigen expression to very high CT expression. This shift is accompanied by modifications of T200 eventually leading to a T200 protein profile identical to that of CTL clones. However, MLC cells propagated without the addition of IL 2-containing supernatants do not undergo a shift in CT antigen expression. Thus, the extent to which modifications occur in the T200 molecule is regulated by soluble factors. Competitive binding assays with two CT-specific MAb indicated that at least two distinct but overlapping neo-epitopes appear as the result of the T200 alterations. In sum, we have discovered the presence of CTL-lineage-specific activation antigens whose expression is regulated by lymphokines and is linked to cytolytic function. MAb specific for determinants such as these could be invaluable tools in the enumeration and depletion of specific T cell subsets in in vivo situations.