Final answer:
The endogenous antigen presentation pathway processes intracellular antigens using proteasomes and the TAP system to display them on MHC I molecules, which are found on all nucleated cells, to T cells.
Step-by-step explanation:
Endogenous Antigen Presentation via MHC I
The endogenous antigen presentation pathway involves the processing and presenting of intracellular antigens, typically from viruses or other intracellular pathogens, to the immune system. Normal cell proteins and pathogen-specific proteins are degraded by proteasomes into peptides. These peptides are then transported into the endoplasmic reticulum by the transporter associated with antigen processing (TAP) system. Here, they bind to MHC I molecules and are transported to the cell surface via a transport vesicle for recognition by T cells. Cells that express MHC I molecules include virtually all nucleated cells, allowing the immune system to monitor these cells for signs of infection and, consequently, to induce targeted cell destruction if a foreign antigen is presented.
Professional antigen-presenting cells (APCs) like dendritic cells, macrophages, and B cells can also process and present antigens via MHC I. While MHC II presentation is exclusive to APCs, MHC I presentation is universal in nucleated cells, underscoring the integral role of MHC I in immune surveillance against intracellular pathogens.