Alloantigen-induced T-cell proliferation: Lyt phenotype of responding cells and blocking of proliferation by Lyt antisera.

Cytotoxic T cells of the mouse express Lyt-1 as well as Lyt-2 and -3 on their surface, and T-cell cytotoxicity can be blocked by Lyt-2 and Lyt-3 (but not Lyt-1) antisera in the absence of added complement [Nakayama, E., Shiku, H., Stockert, E., Oettgen, H. F. & Old, L. J. (1979) Proc. Natl. Acad. Sci. USA 76, 1977-1981]. This analysis has now been extended to the study of the Lyt phenotype of T cells responding to alloantigens, concanavalin A (Con A), and phytohemagglutinin (PHA) and the effect of Lyt antibody on T-cell proliferation and the generation of H-2-specific killer T cells. H-2 (D/K and I), Con A, and PHA stimulation was abolished by pretreating responding cell populations with Lyt-1 antiserum and complement. Pretreatment with Lyt-2 or -3 antiserum and complement did not decrease alloantigen or Con A stimulation but did abolish PHA stimulation. Cytotoxic cells were not generated in H-2 alloantigen-primed cultures pretreated with Lyt-1, -2, or -3 antiserum and complement. When responding cells were cultured with Lyt antiserum in the absence of added complement, Lyt-2 or -3 antiserum (but not Lyt-1 antiserum) blocked alloantigen-induced proliferation and delayed generation of killer cells. Under similar conditions, Con A and PHA stimulation was not blocked by Lyt-1,-2, or -3 antiserum. Evidence from these Lyt elimination and blocking tests and from direct Lyt phenotyping of responding cells leads to the following conclusions. Two populations of Lyt(+) cells are involved: Lyt-1(+)2(-)3(-) and Lyt-1(+)2(+)3(+). Current evidence does not favor the existence of Lyt-1(-)2(+)3(+) cells but indicates that pre-killer and killer cells derive from the Lyt-1(+)2(+)3(+) population and have a Lyt-1(+)2(+)3(+) phenotype. H-2 (D/K and I) and PHA stimulation ordinarily activate the Lyt-1(+)2(+)3(+) population, whereas Con A and I region or Mls locus antigens activate the Lyt-1(+)2(-)3(-) population. However, when Lyt-1(+)2(+)3(+) cells are eliminated or blocked by Lyt-2 or -3 antiserum, H-2 alloantigen stimulation leads to proliferation of the Lyt-1(+)2(-)3(-) population. Blocking of H-2-induced proliferation by Lyt-2 or -3 antiserum adds further support to the possibility that molecules bearing Lyt-2 and -3 determinants are involved in T-cell recognition.