Constitutive expression of IL-7 receptor alpha does not support increased expansion or prevent contraction of antigen-specific CD4 or CD8 T cells following Listeria monocytogenes infection.
Expression of IL-7Ralpha (CD127) has been suggested as a major determinant in the survival of memory T cell precursors. We investigated whether constitutive expression of IL-7Ralpha on T cells increased expansion and/or decreased contraction of endogenous Ag-specific CD4 and CD8 T cells following infection with Listeria monocytogenes. The results indicate that constitutive expression of IL-7Ralpha alone was not enough to impart an expansion or survival advantage to CD8 T cells responding to infection, and did not increase memory CD8 T cell numbers over those observed in wild-type controls. Constitutive expression of IL-7Ralpha did allow for slightly prolonged expansion of Ag-specific CD4 T cells; however, it did not alter the contraction phase or protect against the waning of memory T cell numbers at later times after infection. Memory CD4 and CD8 T cells generated in IL-7Ralpha transgenic mice expanded similarly to wild-type T cells after secondary infection, and immunized IL-7Ralpha transgenic mice were fully protected against lethal bacterial challenge demonstrating that constitutive expression of IL-7Ralpha does not impair, or markedly improve memory/secondary effector T cell function. These results indicate that expression of IL-7Ralpha alone does not support increased survival of effector Ag-specific CD4 or CD8 T cells into the memory phase following bacterial infection.