Lyt-2 and lyt-3 antigens are on two different polypeptide subunits linked by disulfide bonds. Relationship of subunits to T cell cytolytic activity.

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Abstract
Lyt-2 and Lyt-3 antigens are carried on separate disulfide-bonded subunits of the same cell surface macromolecules. These are present on [mouse] thymocytes in a variety of multimeric forms consisting of disulfide-bonded dimers, tetramers and hexamers of pairwise combinations of 3 subunits (30,000, 34,000 and 38,000 MW). From reduced and alkylated Nonidet-P40 thymus extracts, a monoclonal anti-Lyt-2 antibody precipitates both the 38,000 and 34,000 MW subunits, but not the 30,000 MW subunit. Almost all of the Lyt-2 and Lyt-3 subunits on the cell are covalently linked by disulfide bonds. Small amounts of the free Lyt-3 subunit was seen in some experiments. Similarly, small amounts of Lyt-2+3- material, consisting of dimers of the 38,000 and 34,000 MW subunits were identified. Each of the 3 subunits migrated with a basic charge (pI [isoelectric point] > 8) on 2-dimensional gels. Cytotoxic effector cells that are blocked by anti-Lyt-2 and anti-Lyt-3 can be treated with trypsin and other arginine-specific proteases to remove these antigens. At low concentrations of these proteases, Lyt-3 antigens are selectively removed. After selective removal of Lyt-3 antigens, cytotoxic effector cells are still active and blocking of activity by anti-Lyt-3 antigens, cytotoxic effector cells are still active and blocking of activity by anti-Lyt-3 is significantly reduced; blocking of activity by anti-Lyt-2 is significantly increased. Neither Lyt-2 nor Lyt-3 is allelically excluded on thymocytes or T cells. The Lyt-2,Lyt-3 macromolecules probably are associated with but do not serve as the T cell antigen receptor.

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