To study T cell exhaustion in leukemia, Chen et al. generated a TCR-transgenic mouse specific for a currently unknown leukemia antigen (TCRTg101). Adoptively transferred TCRTg101 cells did not extend survival of leukemia-bearing mice, suggesting dysfunction. As TCRTg101 cells proliferated, they acquired molecular and transcriptional features of exhaustion (PD-1, LAG-3, Tox) and lost functionality (cytokine secretion and lytic ability). This phenotype, mediated through direct antigen presentation by leukemia cells, was largely irreversible; proliferated TCRTg101 cells from diseased hosts did not expand in a secondary host or respond to anti-PD-1/LAG-3.
Contributed by Alex Najibi
ABSTRACT: The existence of a dysfunctional CD8(+) T cell state in cancer is well established. However, the degree to which CD8(+) T cell fates are influenced by the context in which they encounter cognate tumor antigen is less clear. We previously demonstrated that CD8(+) T cells reactive to a model leukemia antigen were deleted by antigen cross-presenting type 1 conventional dendritic cells (cDC1s). Here, through a study of T cell receptor (TCR) transgenic CD8(+) T cells (TCR(Tg101)) reactive to a native C1498 leukemia cell antigen, we uncover a different mode of T cell tolerance in which TCR(Tg101) undergo progressive expansion and differentiation into an exhausted state. Antigen encounter by TCR(Tg101) requires leukemia cell major histocompatibility complex (MHC)-I expression and is independent of DCs, implying that leukemia cells directly mediate the exhausted TCR(Tg101) phenotype. Collectively, our data reveal that leukemia antigens are presented to CD8(+) T cells via discrete pathways, leading to distinct tolerant states.
