Transmission of survival signals through Delta-like 1 on activated CD4+ T cells

Notch expressed on CD4+ T cells transduces signals that mediate their effector functions and survival by interacting with Notch ligands on adjacent cells. Although Notch signaling is known to be cis-inhibited by Notch ligands expressed on the same cells, the role of Notch ligands on T cells remain unclear. In this report we demonstrate that the Notch ligand Dll1 on CD4+ T cells transduces signals required for the maintenance of activated CD4+ T cells without affecting Notch signaling in the same cells. T cell-specific Dll1-deficient (Dll1-/-) mice did not show any defect in T cell development in thymus or spleen. Co-transfer of CD4+ T cells from Dll1-/- and control mice into recipient mice followed by immunization revealed a rapid decline of CD4+ T cells from Dll1-/- mice compared with control cells. Dll1-/- mice exhibited lower clinical scores of experimental autoimmune encephalitis than control mice. The expression of Notch target genes in CD4+ T cells from Dll1-/- mice was not affected, suggesting that Dll1 deficiency in T cells does not affect cis Notch signaling. Overexpression of the intracellular domain of Dll1 in Dll1-deficient CD4+ T cells partially rescued impaired survival. Our data highlight Dll1 as an independent regulator of Notch-signaling for the survival of activated CD4+ T cells, and provide new insight into the physiological roles of Notch ligands as well as a regulatory mechanism important for maintaining adaptive immune responses The mRNA expression in activated CD4+ T cells from mouse was obtained by DNA microarray analysis. These mRNA expression was compared.