Chapter 28: Immune Disorders and Antimicrobial Therapy

Immune disorders arise when immune responses become harmful or insufficient, as seen in hypersensitivity reactions, autoimmune diseases, and immunodeficiency conditions. Immediate hypersensitivity reactions involve IgE mediated activation of mast cells that release inflammatory mediators responsible for allergic symptoms and potentially life threatening anaphylaxis, while delayed type hypersensitivity reactions are cell mediated responses driven by T helper cells that cause tissue inflammation after repeated antigen exposure. Autoimmune diseases occur when the immune system mistakenly targets self antigens, leading to organ specific or systemic conditions such as type 1 diabetes or systemic lupus erythematosus. In contrast, immunodeficiency disorders result from weakened immune defenses, either through genetic defects such as severe combined immunodeficiency or acquired conditions such as human immunodeficiency virus infection that destroys T helper cells and predisposes individuals to opportunistic infections. Disease prevention is achieved through vaccination, which stimulates adaptive immunity and immunological memory using various vaccine technologies including inactivated, attenuated, toxoid, subunit, conjugate, recombinant, and nucleic acid vaccines. Therapeutic manipulation of immune responses through immunotherapy has become an important strategy in modern medicine, particularly in cancer treatment through approaches such as checkpoint inhibitors and engineered T cell therapies that enhance immune recognition of tumor cells. The chapter also describes antimicrobial drugs used to treat infectious diseases, including antibiotics that inhibit bacterial cell wall synthesis, protein synthesis, nucleic acid synthesis, or metabolic pathways, as well as antiviral, antifungal, and antiparasitic agents that target pathogen specific biological processes. Finally, the chapter addresses the growing global challenge of antimicrobial resistance, which arises through genetic mutations or horizontally transferred resistance genes that enable microorganisms to evade antimicrobial effects through mechanisms such as drug inactivation, reduced permeability, target modification, or efflux systems. Understanding immune disorders, therapeutic interventions, and the evolution of drug resistance is essential for managing infectious diseases and developing new strategies for disease control.