Chapter 14: Immune Responses & Transplant Care

The immune system operates through interconnected pathways involving innate immunity, which provides immediate nonspecific protection, and adaptive immunity, which develops targeted responses through humoral and cell-mediated mechanisms. Central lymphoid organs including bone marrow and thymus generate immune cells, while peripheral lymphoid structures such as lymph nodes and spleen facilitate immune surveillance. Key cellular components include mononuclear phagocytes that process antigens, B lymphocytes that produce immunoglobulin classes with distinct functions, T helper cells that coordinate immune responses, cytotoxic T cells that eliminate infected cells, and natural killer cells that provide immediate defense against malignant and infected cells. The chapter explores pathological immune responses including hypersensitivity reactions classified by mechanism and timing, autoimmune disorders where immune tolerance fails resulting in self-tissue damage, and immunodeficiency states that compromise host defense. Clinical management of allergic disorders involves allergen avoidance strategies, pharmacological interventions including antihistamines and corticosteroids, and immunotherapy protocols. Transplantation immunology requires understanding human leukocyte antigen compatibility, crossmatching procedures, and rejection patterns ranging from hyperacute vascular rejection to chronic allograft dysfunction. Immunosuppressive therapy protocols utilize calcineurin inhibitors to block T cell activation, cytotoxic agents to prevent lymphocyte proliferation, and monoclonal antibodies for targeted immunomodulation. The chapter addresses graft-versus-host disease mechanisms in stem cell transplantation and age-related immunosenescence effects on clinical outcomes.