MHCI, or Major Histocompatibility Complex class I, is a set of cell surface proteins essential for the immune system to recognize foreign molecules. It presents endogenous peptides, typically derived from intracellular proteins, to CD8+ cytotoxic T cells, facilitating the detection and elimination of infected or cancerous cells. By presenting these peptides, MHCI plays a crucial role in immune surveillance and response. Its proper functioning is vital for maintaining immune system balance and preventing autoimmune diseases.