42: The Immune System Last updated Save as PDF Page ID 12634 Boundless Boundless 42.1: Innate Immune Response - Innate Immune Response The immune system serves to defend against pathogens: microorganisms that attempt to invade and cause disease in a host. 42.2: Innate Immune Response - Physical and Chemical Barriers The innate immune response has physical and chemical barriers that exist as the first line of defense against infectious pathogens. 42.3: Innate Immune Response - Pathogen Recognition Upon pathogen entry to the body, the innate immune system uses several mechanisms to destroy the pathogen and any cells it has infected. 42.4: Innate Immune Response - Natural Killer Cells Natural killer cells are part of the innate immune response that recognize abnormal MHC I molecules on infected/tumor cells and kill them. 42.5: Innate Immune Response - The Complement System Around 20 soluble proteins comprise the complement system, which helps destroy extracellular microorganisms that have invaded the body. 42.6: Adaptive Immune Response - Antigen-presenting Cells- B and T cells B and T cells, parts of the adaptive immune response, contain receptors that can identify antigens derived from pathogens. 42.7: Adaptive Immune Response - Humoral Immune Response The humoral immune response defends against pathogens that are free in the blood by using antibodies against pathogen-specific antigens. 42.8: Adaptive Immune Response - Cell-Mediated Immunity Cell-mediated immunity involves cytotoxic T cells recognizing infected cells and bringing about their destruction. 42.9: Adaptive Immune Response - Cytotoxic T Lymphocytes and Mucosal Surfaces The lymphatic system houses large populations of immune cells which are released upon detection of a pathogen. 42.10: Adaptive Immune Response - Immunological Memory Immunological memory allows the adaptive immune system to very rapidly clear infections that it has encountered before. 42.11: Adaptive Immune Response - Regulating Immune Tolerance Immune tolerance of self and harmless antigens occurs by deleting B and T cells that recognize those antigens, often near mucosal surfaces. 42.12: Antibodies - Antibody Structure Variations in antibody structure allow great diversity of antigen recognition among different antibodies. 42.13: Antibodies - Antibody Functions Antibodies, part of the humoral immune response, are involved in pathogen detection and neutralization. 42.14: Disruptions in the Immune System - Immunodeficiency Immunodeficiency occurs when the immune system cannot appropriately respond to infections. 42.15: Disruptions in the Immune System - Hypersensitivities Hypersensitivities are maladaptive immune reactions against harmless antigens (allergies) or against self antigens (autoimmunity).