The immune response to pathogens

Every day your body is attacked by pathogens, yet most of the time you never notice — because your immune system deals with them quietly and precisely. In this lesson we follow the whole story of the immune response, one careful step at a time. We start with antigens, the molecular name-badges that let your body tell its own self cells from foreign non-self invaders. We watch phagocytes — macrophages and neutrophils — hunt down and destroy pathogens by phagocytosis: recognition, engulfing into a phagosome, fusion with a lysosome, and digestion by enzymes. Then we meet the specific primary immune response: the macrophage presenting antigen as an APC, T-helper cells releasing cytokines, B-lymphocytes and plasma cells pouring out antibodies, and T-killer cells destroying infected cells. Finally we see why memory cells make the secondary response so much faster and stronger, giving you long-term immunity — the very principle behind vaccination.