LIGHT-deficiency impairs CD8+ T cell expansion, but not effector function

Abstract

LIGHT, a newly identified member of the tumor necrosis factor (TNF) family, is expressed on activated T lymphocytes. To evaluate how LIGHT contributes to T cell functions, we generated LIGHT-deficient (LIGHT-/-) mice using gene targeting. Disruption of LIGHT significantly reduced CD8+ T cell-cycle progression, leading to reduced proliferation to anti-CD3, anti-CD3/anti-CD28 or allogeneic stimulation, whereas proliferation of CD4+ T cells remained unchanged. In contrast to the observed proliferative defects, isolated CD8+ T cells from LIGHT-/- mice displayed normal cytotoxic effector function development when compared to wild-type CD8+ T cells. Underlying a potential mechanism of reduced CD8+ T cell proliferation, LIGHT-/- CD8+ T cells displayed reduced surface levels of CD25 and a diminished ability to proliferate in response to exogenous IL-2. Furthermore, addition of IL-12 to LIGHT-/- CD8+ T cell cultures could not ameliorate this proliferative defect. These results reveal a potential mechanism of action for LIGHT as a positive regulator of CD8+ T cell expansion, but not lytic effector function development.