Requirement for non T-cells in the generation of cytotoxic T lymphocytes (CTL) in vitro. II. Characterization of the active cells in the spleen of nude mice.

Small numbers of LN cells will produce many more cytotoxic lymphocytes on in vitro culture with allogeneic stimulator cells if spleen cells from nu/nu mice are also present throughout the culture period. All cytotoxic cells produced are T cells and arise from precursors in the LN component. The nude spleen component appears to be providing a required non-T cell which has been lost from the LN component through dilution. At least two active subpopulations of cells, differing in sedimentation velocity, adherence properties, radiation sensitivity, and antigen recognition properties can be identified in the nu/nu spleen. The first, the dominant activity in normal nu/nu spleen, is nonadherent, radiation sensitive, and can synergize with either syngeneic or allogeneic LN cells provided both are different from the same alloantigens in the stimulator population. The second, found in nu/nu spleen cells precultured with alloantigen, sediments more rapidly, is adherent, and radiation resistant, and need not be allogeneic to the stimulator cells to synergize with LN cells. The first subpopulation may give rise to the second.