Lymphotactin acts as an innate mucosal adjuvant

Lymphotactin (Lptn) is a C chemokine produced predominantly by NK and CD8-positive (CD8+) T cells including gammadelta TCR-positive (TCR+) intraepithelial lymphocytes. Lptn is chemotactic for NK and T cells and likely plays an important role in maintaining the integrity of the epithelium and in mucosal immune responses. In this study, we characterized the immune responses to OVA given intranasally with Lptn to mice. This regimen enhanced OVA-specific serum Ab responses and Ab titers in mucosal secretions. Lptn also enhanced OVA-specific Ab-forming cells in mucosal and systemic compartments. CD4-positive (CD4+) T cells isolated from mucosal compartments and spleens of mice intranasally immunized with OVA plus Lptn displayed higher OVA-specific proliferative responses and greater synthesis of IFN-gamma, IL-2, IL-4, IL-5, IL-6, and IL-10 than did CD4+ T cells from mice given OVA without Lptn. These studies indicate that Lptn has adjuvant properties and suggest that Lptn present in the mucosa has the potential to enhance mucosal and systemic Ab responses through help provided by Th1- and Th2-type cells to link the initial innate signals of the mucosa with the acquired immune system.