Antigen presentation and T-cell activation. Animation showing the process of antigen presentation in a cell infected by a virus, followed by the activation of a cytotoxic T-cell (Tc cell). The animation starts with the infected cell (grey, bottom) and a Tc cell (orange, top). Within the infected cell is the nucleus (bottom), a virus (red, centre left), a proteasome (pink, centre left), the endoplasmic reticulum (white, centre), and the Golgi apparatus (yellow, upper centre). Within the endoplasmic reticulum is a major histocompatibility complex molecule (MHC I, blue) with a stabilising protein (red). The MHC I molecule is held here until the arrival of an antigen. The process starts with viral proteins (red strands) being degraded by the proteasome to produce viral peptides (red triangles). These act as antigens, binding to the MHC I molecule. The stabilising protein disassociates and the resulting MHC Iâpeptide complex is transported (red arrows) to the cell membrane via the Golgi apparatus. This complex then binds to a receptor molecule (green) on the surface of the Tc cell. A co-receptor CD8 (white) binds to the CMH I molecule, enabling the secretion of toxins that kill the infected cell. For this animation without labels, see K004/4172. |