T cells get by with a little help from their friends
In animal models, lymphocytic choriomeningitis virus (LCMV) may be controlled after acute infection or may establish various levels of persistence. Cytotoxic responses mediated by CD8+ T cells are responsible for both initial control of LCMV and for immunopathology. As discussed in this article, there is emerging evidence that the levels of antigen to which the immune system is exposed over time are important in controlling CD8+ T cell activation, memory responses and exhaustion, and that these levels are affected by the efficiency of T cell help and the presence of antibody. To enable lasting control of LCMV infection, CD8+ T cells, CD4+ T cell help and B cells are all required. These findings have important implications for the prevention and treatment of infection by viruses such as hepatitis B and C viruses, cytomegalovirus and HIV. © 2004 Wiley-VCH Verlag GmbH & Co. KGaA.