Impact of γ-chain cytokines on EBV-specific T cell cultures

Background: Recent preclinical adoptive immunotherapy studies in murine models prompt to employ "proper" rather than "as many as possible" antigen-specific T cells to gain better therapeutic results. Ideally, "proper" T cells are poorly differentiated in vitro, but retain the capacity to fully differentiate into effector cells in vivo, where they can undergo long-term survival and strong proliferation. Such requirements can be achieved by modifying culture conditions, namely using less "differentiating" cytokines than IL-2. Methods: To evaluate this issue in human T cell cultures, we exploited a well characterized and clinical-grade protocol finalized at generating EBV-specific CTL for adoptive immunotherapy. In particular, we studied the impact of IL 7, IL 15 and IL 21 compared to IL 2 on different aspects of T cell functionality, namely growth kinetics, differentiation/ activation marker expression, cytokine production, and short-term and long-term cytotoxicity. Results: Results disclosed that the culture modifications we introduced in the standard protocol did not improve activity nor induce substantial changes in differentiation marker expression of EBV-specific CTL. Conclusions: Our data indicated that the addition of gamma-chain cytokines other than IL-2 for the generation of EBV-specific T cell cultures did not produce the improvements expected on the basis of recent published literature. This fact was likely due to the intrinsic differences between murine and human models and highlights the need to design ad hoc protocols rather than simply modify the cytokines added in culture.