IMMUNE SYSTEM AND LYMPHATICS

The immune system and lymphatic system together form one of the most complex regulatory networks in human physiology, responsible for the detection, neutralization, and elimination of pathogenic microorganisms, abnormal host cells, and foreign substances. The lymphatic system functions as a major conduit for immune cell trafficking, antigen presentation, and interstitial fluid balance, while the immune system comprises innate and adaptive components with distinct mechanisms and roles. Innate immunity provides non-specific, rapid protection through physical barriers, phagocytes, natural killer cells, complement proteins, and inflammatory mediators. Adaptive immunity provides highly specific responses mediated by T- and B-lymphocytes, with immunological memory enabling more rapid and potent responses upon re-exposure. Disruptions in immune regulation may result in autoimmunity, immunodeficiency, hypersensitivity, or chronic inflammation. Advances such as monoclonal antibodies, immune checkpoint inhibitors, CAR-T cell therapy, and gene-based vaccines have revolutionized the management of infectious, neoplastic, and immune-mediated diseases. This chapter provides an in-depth analysis of immune cell biology, immune responses, mechanisms of autoimmune and immunodeficiency disorders, principles of immunotherapy and vaccination, and scientific foundations relevant to pharmacology and clinical medicine. The discussion is supplemented with comparative tables and conceptual diagrams to facilitate understanding of functional pathways and disease processes.