Induction and visualization of mucosal memory CD8 T cells following systemic virus infection

Whether CD8 T cell memory exists outside secondary lymphoid organs is uncle ar. Using an adoptive transfer system that enables tracking of OVA-specific CD8 T cells, we explored the antigenic requirements for inducing CD8 T cel l memory and identified intestinal mucosa memory cells. Although systemic i mmunization with soluble OVA induced clonal expansion, memory CD8 cells wer e not produced. In contrast, infection with virus-encoding OVA induced memo ry CD8 cells in the periphery and the lamina propria and intraepithelial co mpartments of the intestinal mucosa, Mucosal memory cells expressed a disti nct array of adhesion molecules as compared with secondary lymphoid memory cells, suggesting that there may be separate mucosal and systemic memory po ols. Mucosal CD8 memory cells rapidly produced IFN-gamma after Ag stimulati on, Reactivation of memory cells by Ag feeding resulted in increased cell s ize and up-regulation of CD28 and CD11c, CD8 mucosal memory cells exhibited ex vivo lytic activity that was up-regulated dramatically following Ag ree ncounter in vivo, Interestingly, reactivation of memory cells did not requi re CD28-mediated costimulation, The ability of the intestinal mucosa to mai ntain CD8 memory cells provides a potential mechanism for effective mucosal vaccination.