T-cell clones with L3T4-positive or Lyt-2-positive phenotypes responding to mutant MHC class II antigen and inducing graft versus host reaction.

Two types of T cell clones responding to mutant major histocompatibility class II antigen (Iabm12) were established from spleen cells of C57BL/6 mice: one was L3T4-positive and the other Lyt-2-positive. These two types of clones carried functionally different properties. Lyt-2+ clones were absolutely dependent on exogenous interleukin-2 for their proliferation, whereas some L3T4+ clones secreted interleukin-2 and proliferated autonomously. Both types of clones had cytotoxic activities to bm12 target cells, and Lyt-2+ clones showed stronger activities than L3T4+ clones. Lyt-2+ clones induced induration in situ, whereas the L3T4+ clones induced ulcerative reaction when injected intradermally into mice. Histologically, the L3T4+ clones caused necrosis of the epidermis or upperdermis, while the Lyt-2+ clones induced infiltration of small round cells through the epidermis to the subcutaneous tissues and caused thickening of the epidermis. These characteristic reactivities might be due to a difference in lymphokines produced by each type of T cell subset in response to Iabm12 antigen.