Culture-differentiated CD8(+) T cells acquire innate memory-like traits and respond to a pathogen-associated molecule.

Selection of conventional CD4(+) or CD8(+) T cells is usually driven by the interaction of double-positive CD4(+)CD8(+) thymocytes with epithelial cells. Here, we demonstrate preferential selection of CD8(+) thymocytes from in vitro differentiation of CD4(+)CD8(+) double-positive thymocytes exhibiting the characteristics of nonconventional innate memory CD8(+) cells. In contrast to conventional CD8(+) thymocytes, these culture-differentiated CD8(+) cells are eomesodermin positive and robustly express CXCR3, CD44, CD122 and TLR2. Interestingly, the pathogen-associated molecule porin promotes preferential differentiation of the CD8(+) single-positive subset in association with promyelocytic leukemia zinc-finger upregulation and interleukin (IL)-4 production. On priming with anti-CD3 antibody, porin augmented TLR2 and IFN-γ indicating a role of the TLR ligand in acquisition of innate memory response of CD8(+) thymocytes. In addition, porin has a cooperative role with IL-15 on the expansion of memory-phenotype CD8(+) T cells along with its effector function. Thus, the study opens an avenue to unfold the cues for development of these cells and the strategies adopted for bolstering immunity during primary infection.