Cytotoxic T lymphocyte activation by cross-priming

Cross-priming represents the induction of cytotoxic T lymphocyte responses to exogenous, usually cell associated, antigens that are captured and re-pr esented on bone-marrow-derived antigen-presenting cells. For effective cros s-priming, cytotoxic T lymphocytes require help from : CD4(+) T cells, whic h mediate this help indirectly via; modification of the antigen-presenting cell. Recent advances made in research,into the cellular and molecular inte ractions required for cross-priming have greatly improved our understanding of the antigenic requirements for effective priming and have revealed a ro le for CD40 and its ligand in the provision of T cell help.