Innate & Adaptive Immunity, Inflammation, T & B Cells, Antibody | Week 2 | NPTEL Immunology 2026

This lecture, part of the NPTEL Immunology course, provides a comprehensive overview of the immune system, focusing on innate and adaptive immunity. It begins with the four barriers of innate immunity (anatomic, physiological, phagocytic, and inflammatory), detailing the roles of key cells like neutrophils, macrophages, dendritic cells, and mast cells. The process of phagocytosis and antigen presentation via MHC class I and II is explained, along with the recognition of PAMPs and DAMPs by pattern recognition receptors such as Toll-like receptors. The inflammatory response is covered in depth, including neutrophil extravasation steps (rolling, activation, adhesion, transmigration) and chemical mediators like histamine, prostaglandins, and leukotrienes. The lecture then transitions to adaptive immunity, distinguishing cell-mediated (T cells) and humoral (B cells) branches. T cell maturation in the thymus, activation in lymph nodes, and subsets (Th1, Th2, Th17, Treg, Tfh) are discussed. B cell activation in germinal centers, somatic hypermutation, affinity maturation, class switching, and antibody functions are also covered. The complement system and cytotoxic T cell killing mechanisms are briefly introduced. The session includes MCQs for self-assessment and a Q&A segment, reinforcing key concepts. Overall, it serves as a solid foundation for understanding hypersensitivity, autoimmunity, and vaccine immunology in later classes.