Final answer:
Intracellular antigens are presented with class I MHC to CD8 T cells, and extracellular antigens are presented with class II MHC to CD4 T cells, with CD4 and CD8 acting as co-receptors for specific T cell-APC interactions.
Step-by-step explanation:
In general, intracellular antigens are presented associated with class I MHC to CD8 T cells and extracellular antigens are presented with class II MHC to CD4 T cells.
Both CD4 and CD8 are referred to as co-receptors and are crucial for the specific interaction between T cells and antigen-presenting cells (APCs). CD8+ T cells, which include cytotoxic T lymphocytes, interact with MHC I molecules on APCs or nucleated cells infected with an intracellular pathogen to trigger an immune response. Conversely, CD4+ T cells, which comprise helper T cells and regulatory T cells, are activated by APCs presenting antigens associated with MHC II molecules, leading them to stimulate other immune cells or produce cytokines.