MTS-32 monoclonal antibody defines CD4+8- thymocyte subsets that differ in their maturation level, lymphokine secretion, and selection patterns.

We have previously described MTS-32 as identifying an Ag on both thymic stromal cells and thymocytes. In contrast with CD4+8+ and CD4-8+ thymocytes, of which the vast majority are MTS-32+, a notable subset of CD4+8- thymocytes is MTS-32-. Here we show that with regard to heat-stable Ags, Qa-2, and CD69 expression CD4+8- MTS-32- thymocytes are phenotypically enriched in mature cells when compared with their MTS-32+ counterparts. Moreover, sorted CD4+8- MTS-32+ thymocytes are unable to respond to anti-CD3 cross-linking, whereas MTS-32- CD4+8- thymocytes respond to the same stimulus by producing IL-4, IL-5, IL-10, IFN-gamma, and trace amounts of IL-2. In addition, MTS-32- CD4+8- and CD4-8- TCR-alpha beta+ thymocytes differ in their TCR V beta repertoire on a Mls-1a selecting background. We therefore suggest that the MTS-32 ligand is involved in signals consecutive with TCR recognition in the thymus, i.e., selection, activation, and lymphokine production.