Stable expression of Lyt-2 homodimers on L3T4+ T cell clones.

The murine T lymphocyte antigen Lyt-2 is considered to act as an accessory molecule to the class I-restricted T cell receptor during antigen recognition. We have previously described two unusual Lyt-2+L3T4+ class II-restricted T cell clones whose activation by antigen is inhibited by antibodies to L3T4 but not to Lyt-2 (B. Fazekas de St. Groth et al., Proc. Natl. Acad. Sci. USA 1986. 83: 2594). The Lyt-2 immunoprecipitated from one of these clones was indistinguishable from the molecule found on splenic T cells, as analyzed under reducing conditions on polyacrylamide gels, in two-dimensional charge/size separations and in peptide mapping. The molecule from the second clone showed slightly more extensive glycosylation but was within the range described for functional Lyt-2 on cytotoxic T cell lines. Lyt-2 mRNA from both clones showed no abnormalities on Northern analysis. Lyt-2 is normally expressed on thymocytes and peripheral T cells as a heterodimer disulfide bonded to the Lyt-3 glycopeptide, yet Lyt-3 could not be detected on the cell membranes of our clones; Lyt-2 existed as stable homodimers without Lyt-3. Thus Lyt-3 is not required structurally for the spontaneous expression of Lyt-2 on lymphoid cells.