Regulation of a cytotoxic response toward alloantigens by T-amplifier and non-T-suppressor cells.

A system is described by which it is possible to generate in vitro non-specific T-amplifier and non-T-suppressor cells without accompanying formation of CTL. Such cells could be separated and tested for their capacity to regulate generation of CTL towards H-2 alloantigen. The experimental setup was as follows: M-locus or syngeneically activated spleen cells were fractionated on BSA-gradients and added to fresh, nylon wool purified (T) precursors. These cultures were stimulated during a second stage with H-2 alloantigen and lytic activities monitored with the chromium release assay. It was found that M-locus activated cells contained two separable subpopulations: 1) an anti-Thy 1 sensitive, non-adherent amplifier cell of intermediate density and 2) a blast cell which was insensitive to anti-Thy 1 as well as RaMIg treatment (i.e. a “null” cell). This cell was adherent, but non-phagocytosing and had strongly suppressive effects on the generation of CTL. It also suppressed—at least partially—the activity of fully differentiated CTL. In syngeneically stimulated cultures strongly enhancing T amplifier cells with blast cell characteristics were found.