Nab2 regulates secondary CD8+ T-cell responses through control of TRAIL expression.

CD4(+) Th cells are pivotal for the generation and maintenance of CD8(+) T-cell responses. "Helped" CD8(+) T cells receive signals during priming that prevent the induction of the proapoptotic molecule TNF-related apoptosis-inducing ligand (TRAIL) during reactivation, thereby enabling robust secondary expansion. Conversely, "helpless" CD8(+) T cells primed in the absence of Th induce TRAIL expression after restimulation and undergo activation-induced cell death. In the present study, we investigated the molecular basis for the differential regulation of TRAIL in helped versus helpless CD8(+) T cells by comparing their transcriptional profiles, and have identified a transcriptional corepressor, NGFI-A binding protein 2 (Nab2), that is selectively induced in helped CD8(+) T cells. Enforced expression of Nab2 prevents TRAIL induction after restimulation of primary helpless CD8(+) T cells, and expression of a dominant-negative form of Nab2 in helped CD8(+) T cells impairs their secondary proliferative response that is reversible by TRAIL blockade. Finally, we observe that the CD8(+) T-cell autocrine growth factor IL-2 coordinately increases Nab2 expression and decreases TRAIL expression. These findings identify Nab2 as a mediator of Th-dependent CD8(+) T-cell memory responses through the regulation of TRAIL and the promotion of secondary expansion, and suggest a mechanism through which this operates.