Final answer:
MHC-I molecules present antigens from intracellular pathogens for detection by CD8 T cells, leading to the destruction of infected or abnormal cells by the immune system.
Step-by-step explanation:
The purpose of MHC-I molecules is critical for the immune system. They are expressed on all nucleated cells and present normal "self" antigens as well as foreign antigens when a cell is infected. If infected with intracellular pathogens like viruses, the cell's MHC-I molecules will display pieces of the pathogen (antigens) on the cell surface. This is a signal for cytotoxic T cells, which have CD8 receptors, to recognize and destroy the infected cells.
Cytotoxic T cells play a pivotal role in the immune response by targeting and killing cells that display foreign antigens via their MHC-I molecules. Viruses and tumor cells may interfere with this process by lowering the presence of MHC-I on the cell surface or by presenting deformed MHC-I molecules, which can also alert NK cells to destroy the abnormal cell.
Overall, the interaction between MHC-I molecules and CD8 T cells is essential for the detection and elimination of cells harboring intracellular pathogens or exhibiting tumor-like characteristics, thereby maintaining the health of the organism.