Cutting edge:: Limiting amounts of IL-7 do not control contraction of CD4+ T cell responses

During the acute T cell response most effector T cells die while some survive and become memory T cells. Selective expression of CD127 (IL-7R alpha) on effector T cells has been proposed to engender their survival into the memorypool, We assessed the role of IL-7 in effector T cell survival using MHC class II tetramers to track a CD4(+) T cell response following infection with a recombinant vaccinia virus (rVV-2W1S). Exogenous IL-7 prevented the contraction of the 2W1S-specific CD4(+) T cell response after rVV-2W1S infection. IL-7 increased proliferation of, and Bcl-2 expression within, 2W1S-specific T cells; the latter was required for IL-7-driven prevention of contraction. Conversely, in vivo neutralization of IL-7 or Bcl-2 did not exacerbate the contraction of 2WIS-specific CD4(+) T cells. These data suggest that IL-7 administration may enhance the survival of effector T cells but that IL-17 is not the limiting factor during normal contraction of the response.