The Lyt phenotype of a long-term allospecific T cell line. Both helper and killer activities to IA are mediated by Ly-1 cells.

The relationship between surface antigen expression and function in the long-term allospecific T cell line C.C3.11.75 was examined by flow microfluorometry, antiserum plus complement depletion and cell sorting. T cells of the line expressed Lyt-1, but little or no Lyt-2 antigens. Proliferation to cells bearing Iak determinants, generation of T cell-replacing nonspecific helper factor in response to Iak-positive cells and the killing of Iak-positive targets were dependent only on Ly-1 cells. No obvious heterogeneity was found in this cell line despite its disparate functional activities. The fact that Lyt-2 molecules need not be present for killing directed against Ia determinants indicates that such molecules are not obligatory for the induction or delivery of killing and raises the question of what the role of Lyt molecules in T cell recognition or function might be.