CD80 and leukemia: LEX-CD8086 can be taken up by activated CD4+ T cells and CD4+ T cells can acquire exosomal pMHC I and costimulatory molecules from LEX-CD8086 and induce leukemia cell antigen-specific CD8+ T cell responses via pMHC I/TCR (Signal I), CD40L and CD80,CD86 costimulations (Signal II), and IL-2 secretion (Signal III) (40), Figure 7).