An essential role for type 1 interferon-gamma in terminating persistent viral infection

The mechanism(s) by which infectious material is cleared by the host is an area of intensive study. This is especially so with the realization that persistent viral infection is a cause of chronic disease in humans and presents a major health problem. We have used the murine model of infection with lymphocytic choriomeningitis virus to evaluate immune clearance. Mice with a targeted disruption of the IFN-gamma gene mount effective cytotoxic T lymphocyte (CTL) responses after an acute viral challenge and clear virus. CD4+ T cells are not required but CD8+ T cells are mandatory. In contrast, CTL from mice with targeted disruption of the IFN-gamma gene are unable to clear virus from persistently infected mice. In addition to the requirement for IFN-gamma, CD4+ T cells are essential for maintaining a CD8(+)-mediated cure of persistent viral infection.

TCR gamma delta cells: mysterious cells of the immune system

Gamma delta cells participate in pathogenic infections and autoimmune conditions, yet, almost a decade after their discovery, little is known regarding their TCR repertoire or effector functions. Unlike MHC-restricted antigen recognition employed by TCR alpha beta cells, TCR gamma delta cells can recognize whole unprocessed antigens in an MHC- independent manner. The nature of positive and negative selection used to shape the repertoire of TCR gamma delta cells is unclear, especially in the nonlymphoid tissues where these cells predominate. While TCR gamma delta cells express an activated phenotype and are present in pathological conditions, their roles in immunological protein is unknown. This review will focus on our efforts to study these issues of TCR gamma delta biology.