The Costimulatory Molecule CD27 Maintains Clonally Diverse CD8+ T Cell Responses of Low Antigen Affinity to Protect against Viral Variants

SummaryCD70 and CD27 are costimulatory molecules that provide essential signals for the expansion and differentiation of CD8+ T cells. Here, we show that CD27-driven costimulation lowered the threshold of T cell receptor activation on CD8+ T cells and enabled responses against low-affinity antigens. Using influenza infection to study in vivo consequences, we found that CD27-driven costimulation promoted a CD8+ T cell response of overall low affinity. These qualitative effects of CD27 on T cell responses were maintained into the memory phase. On a clonal level, CD27-driven costimulation established a higher degree of variety in memory CD8+ T cells. The benefit became apparent when mice were reinfected, given that CD27 improved CD8+ T cell responses against reinfection with viral variants, but not with identical virus. We propose that CD27-driven costimulation is a strategy to generate memory clones that have potential reactivity to a wide array of mutable pathogens.

Graphical AbstractFigure optionsDownload full-size imageDownload high-quality image (187 K)Download as PowerPoint slideHighlights► CD70 and CD27 enable proliferation and survival of low-affinity CD8+ T cells ► CD27 maintains effector and memory CD8+ T cells of low affinity in vivo ► CD27 establishes enhanced clonal diversity in the memory CD8+ T cell pool ► CD27 enhances recall responses against variant, but not identical, viral epitopes