Memory CD8(+)T cells in heterologous antiviral immunity and immunopathology in the lung

A potent role for memory CD8(+) T cells in heterologous immunity was shown with a respiratory mucosal model of viral infection. Memory CD8(+) T cells generated after lymphocytic choriomeningitis virus (LCMV) infection were fu nctionally activated in vivo to produce interferon-gamma (IFN-gamma) during acute infection with vaccinia virus (VV). Some of these antigen-specific m emory cells selectively expanded in number, which resulted in modulation of the original LCMV-specific T cell repertoire. In addition, there was an or gan-selective compartmental redistribution of these LCMV-specific T cells d uring VV infection. The presence of these LCMV-specific memory T cells corr elated with enhanced VV clearance, decreased mortality and marked changes i n lung immunopathology. Thus, the participation of pre-existing memory T ce lls specific to unrelated agents can alter the dynamics of mucosal immunity and disease course in response to a pathogen.