Introduction: The transcription factors Eomesodermin (Eomes) and T-bet are thought to play critical roles in CD8+ effector memory T cell development.  However, the role of Eomes in alloreactive CD8+T cells is not well known. We have previously shown that reduced Eomes expression and upregulation of CTLA4 by CD8+T cells in renal allograft recipient monkeys is associated with attenuation of donor-reactive memory T cell responses and prolonged graft survival. We hypothesized that Eomes expression might be associated with enhanced effector/cytotoxic function by human and non-human primate (NHP) alloreactive CD8+T cells.
Methods: Human and NHP Tcells were purified from peripheral blood mononuclear cells (PBMC) and then co-cultured with irradiated T-cell depleted allogeneic PBMC. Allo-activated CD8+T cells were evaluated by flow cytometry for expression of Eomes, T-bet and CTLA4. Proliferation, intracellular cytokines (IL2, INFγ and TNFα), and Granzyme B following allo-activation were also assessed.
Results: Non-activated human Eomeshi CD8+ T cells, exhibited higher T-bet expression and comprised more IFNγ+, TNFα+ and granzyme-B+, but less IL-2+ cells than Eomes-/lo cells. Non-activated rhesus Eomeshi CD8+T cells, although exhibited low T-bet expression, comprised more IFNγ+ and IL-2+, equivalent TNFα+, but less granzyme-B+ cells than Eomes-/lo cells. After allo-stimulation human Eomeshi population comprised more IFNγ+, TNFα+ and granzyme-B+ cells and a variable proportion of IL-2+ cells. Rhesus Eomeshi cells comprised more IFNγ+ and TNFα+, but less IL-2+, and a variable proportion of granzyme-B+ cells. Human EomeshiT-bethi CD8+T cells exhibited the highest incidence of IFNγ+TNFα+ cells, while rhesus EomeshiT-betlo CD8+T cells exhibited the highest incidence of IFNγ+TNFα+ cells. Following allo-activation there was an inverse correlation between CTLA4 and Eomes expression in NHP but not in human CD8+ T cells.
Conclusion: These data suggest that alloreactive EomeshiCD8+T cells may potentially correlate with anti-donor effector Tmem after transplantation and that phenotypic and functional differences between human and NHP EomeshiCD8+T cells need to be taken into consideration. Eomes may be an important novel biomarker for distinguishing potent alloreactive effector memory T cells.
Yoshihiro Ono. Alan F. Zahorchak. Bala Ramaswami.
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