c-Rel is crucial for lymphocyte proliferation but dispensable for T cell effector function

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Abstract
The TCR signals are essential for T cell activation and proliferation, primarily through the induction of cytokine and cytokine receptors. Several transcription factor families, including NF-κB/Rel, have been implicated in the regulation of cytokine gene expression in T cells in response to antigen, cytokine and mitogenic stimulation. In this study, we show that the mice with a null mutation in the lymphoid-specific c-Rel gene have normal development of lymphoid tissues and T cell compartment. However, T cells derived from the c-Rel knockout mice have several functional abnormalities. The c-Rel-deficient T lymphocytes fail to respond to activation and proliferation signals mediated by the TCR and mitogens in vitro. This is attributed to an impaired production of cytokines IL-2, IL-3 and granulocyte macrophage colony stimulating factor. In addition, the induction of IL-2Rα chain is impaired in the c-Rel–/– T cells. The poor expression of cytokines and IL-2Rα chain correlates with a reduced nuclear translocation of NF-κB components in c-Rel–/– T cells. Since activation is prerequisite for differentiation into effector cells, c-Rel–/– T cells failed to differentiate into cytotoxic T cells or Th cells without rescuing cytokines. However, upon supplement with exogenous IL-2, the c-Rel–/– cytotoxic T lymphocytes are able to execute cytotoxicity and the c-Rel–/– Th cells are capable of providing help to normal B cells. These data suggest that c-Rel is important for inducible cytokine and cytokine receptor expression, and a key regulator of early activation and proliferation in T cells.