The cellular and molecular basis of the Lyt-1+2- T cell-mediated tumor-eradicating mechanism in vivo

This article reviews recent findings that bear on the mechanism(s) of tumor-specific Lyt-1⁺2^? T cell-mediated tumor eradication in vivo A tumor-immune Lyt-1⁺2^? T cell subset has been identified which is distinct from T cells mediating in vitro cytotoxicity (Lyt-1⁺2⁺/1^?2⁺). The Lyt-1⁺2^? cells have a crucial role in rejecting tumor cells when adoptively transferred into T cell-deprived B cell mice. This indicates that Lyt-1⁺2^? T cells do not necessarily require recruitment of the host's cytotoxic T cell precursors for implementation of in vivo immunity. Instead, this T cell subset exerts its anti-tumor effect in collaboration with macrophages as shown with an in vivo tumor cell culture system utilizing a diffusion chamber. A pathway of Lyt-1⁺2^? T cell-macrophage interaction leading to tumor cell killing is discussed in terms of its probable relevance to the eradication of tumor cell masses consisting of tumor cells expressing quantitatively and/or qualitatively different tumor antigens.