Tissue issues: mucosal T-cell responses in HIV-1 infection

Purpose of review This review summarizes our current understanding of HIV-1-specific T-cell responses in mucosal tissues, emphasizing recent work and specifically highlighting papers published over the past 18 months. Recent findings Recent work has improved the standardization of tissue sampling approaches and provided new insights on the abundance, phenotype and distribution of HIV-1-specific T-cell populations in mucosal tissues. In addition, it has recently been established that some lymphocytes exist in tissues as `` permanent resident'' memory cells that differ from their counterparts in blood. Summary HIV-1-specific T-cell responses have been extensively characterized; however, the vast majority of reports have focused on T-cells isolated from peripheral blood. Mucosal tissues of the genitourinary and gastrointestinal tracts serve as the primary sites of HIV-1 transmission, and provide `` front line'' barrier defenses against HIV-1 and other pathogens. In addition, the gastrointestinal tract remains a significant viral reservoir throughout the chronic phase of infection. Tissue-based immune responses may be critical in fighting infection, and understanding these defenses may lead to improved vaccines and immunotherapeutic strategies.