Background

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 development of alloreactive CD8+T cells is not well known. We have previously shown that reduced Eomes expression and upregulation of co-inhibitory cytotoxic T-lymphocyte antigen 4 (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 alloactivated CD8+T cells.

Methods

Human T cells purified from peripheral blood mononuclear cells (PBMC) of healthy volunteers were 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 and intracellular cytokine (INFγ and TNFα), Granzyme B and Perforin production following allo-stimulation were also assessed.

Results

Human CD8+T cells expressed variable levels of Eomes. High Eomes expression by non-activated CD8+T cells correlated with an effector memory phenotype. Eomes^hi CD8+T cells comprised significantly higher percentages of INFγ, TNFα and Granzyme B positive cells, than Eomes^lo CD8+T cells (p<0.05). Following allo-stimulation, the CD8+T cells exhibited wide variability in proliferation of Eomes^hi versus Eomes^lo populations. However, prolonged allo-stimulation was associated with a progressive increase in Eomes expression. Allo-activated Eomes^hi CD8+T cells expressed significantly higher levels of INFγ, TNFα and Granzyme B compared to Eomes^lo CD8+T cells (p<0.05). Both Emoes^hi and Eomes^lo allo-activated CD8+T cells expressed high levels of CTLA4 compared to non-activated CD8+T cells. Concomitant expression of Eomes and T-bet by allo-activated CD8+T cells was associated with significantly higher effector/cytotoxic cells, while lower expression of either Eomes or T-bet was associated with reduced effector/cytotoxic cells.

Conclusions

Irrespective of T-bet expression, higher Eomes expression by allo-activated CD8+T cells is associated with stronger effector/cytotoxic function. Unlike monkeys, upregulation of CTLA4 by human allo-activated CD8+T cells is not associated with downregulation of Eomes. Eomes may be an important novel biomarker for distinguishing human potent alloreactive effector memory T cells.

CITATION INFORMATION: Perez-Gutierrez A, Metes D, Ono Y, Thomson A, Ezzelarab M. High Eomesodermin Expression Correlates with Potent Human Allo-Reactive CD8⁺ Effector T Cells. Am J Transplant. 2017;17 (suppl 3).

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