CD4 and leukemia: To examine whether CD4+ TLEX-CD8086 cells can induce the protective immune against leukemia cells in vivo, DBA/2 mice were immunized with LEX-null, LEX-CD8086, CD4+ TLEX-null cells, CD4+ TLEX-CD8086 cells, and PBS, as a control, for three times, and the mice were then subcutaneously (s.c.)challenged with L1210 cells seven days after the last vaccination.