Slide 1Why is this important?Overview of Adaptive ImmunityOverview of Adaptive ImmunityElements of Adaptive ImmunityThe Tissues and Organs of the Lymphatic SystemLymphatic Vessels and the Flow of LymphLymphoid OrgansAntigensProperties of AntigensProperties and Types of AntigensB Lymphocytes (B Cells) and AntibodiesSpecificity of the B Cell Receptor (BCR)Specificity of the B Cell Receptor (BCR)Specificity and Antibody StructureAntibody FunctionActivation of Complement and InflammationNeutralizationOpsonizationDirect KillingAgglutinationAntibody-Dependent CytotoxicityClasses of AntibodiesClasses of AntibodiesT Lymphocytes (T Cells)Specificity of the T Cell Receptor (TCR)Types of T LymphocytesClonal DeletionImmune Response CytokinesThe Roles of the Major Histocompatibility ComplexAntigen ProcessingAntigen ProcessingCell-Mediated Immune ResponsesCell-Mediated Immune ResponsesCell-Mediated Immune ResponsesMemory T CellsHumoral Immune ResponsesT Dependent Humoral ImmunityT Dependent Humoral ImmunityMemory B Cells and the Establishment of Immunological MemoryMemory B Cells and the Establishment of Immunological MemoryTypes of Acquired ImmunityTypes of Acquired ImmunityM I C R O B I O L O G YWITH DISEASES BY BODY SYSTEM SECOND EDITIONChapter 16Adaptive ImmunityTHIRDWhy is this important?•Two lines of rapid defense against microbial pathogens–First line – skin and mucous membranes–Second line – phagocytosis, interferons, complement, inflammation, and fever•In addition to these nonspecific defenses, our bodies respond specifically to individual microbes•Vaccination is an application of the specific immune responseOverview of Adaptive Immunity•Adaptive immunity is the body’s ability to recognize and defend itself against distinct invaders and their products•Five attributes of adaptive immunity–Specificity–Inducibility–Clonality–Unresponsiveness to self–MemoryOverview of Adaptive Immunity•Involves activity of two main types of lymphocytes (WBC) that act against specific pathogens–B lymphocytes (B cells) – arise and mature in the red bone marrow–T lymphocytes (T cells) – arise in the red bone marrow and mature in the thymus•Two types of adaptive immune responses–Humoral immune responses involve descendants of activated B cells and the antibodies they secrete–Act against extracellular pathogens–Cell-mediated immune responses involve descendants of T cells that regulate adaptive immune responses or attach to intracellular pathogensElements of Adaptive Immunity•Lymphatic system – the organs, tissues, and cells of adaptive immunity•Antigens – the molecules that trigger adaptive immune responses•Antibodies•Chemical signals and mediatorsThe Tissues and Organs of the Lymphatic System•Components constitute a surveillance system that screens the tissues of the body – particularly possible points of entry – for foreign molecules•Lymphatic vessels conduct the flow of lymphLymphatic Vessels and the Flow of Lymph•Form a one-way system that conducts lymph from local tissues and returns it to the circulatory system–Lymph is a liquid with similar composition to blood plasma, which arises from fluid leaked from blood vessels into surrounding tissues•Lymph contains wastes such as degraded proteins and toxins•First collected by lymphatic capillaries, passes into larger lymphatic vessels, and then flows into lymphatic ducts•Lymph only flows toward the heart•Lymph nodes (~1000) house leukocytes that recognize and attach foreigners present in the lymphLymphoid Organs•Primary lymphoid organs – red bone marrow and thymus•Secondary lymphoid organs and tissues – lymph nodes, spleen, tonsils, and MALT–Lymph nodes filter lymph, while the spleen filters blood and removes bacteria, viruses, toxins, and other foreign matter from the blood•MALT includes the appendix; lymphoid tissue of the respiratory tract, vagina, urinary bladder, and mammary glands; and Peyer’s patches in the small intestine–Contains most of the body’s lymphocytesAntigens•Adaptive immune responses are directed against portions of cells, viruses, and even parts of single molecules that the body recognizes as foreign and worthy of attack–These biochemical shapes are known as antigens and they bind to lymphocytes and trigger adaptive immune responsesProperties of Antigens•Properties that make certain molecules more effective at provoking adaptive immunity are a molecule’s shape, size, and complexity–The body recognizes antigens by the 3-D shapes of regions called epitopes (antigenic determinants)•Larger molecules are better antigens•Most effective are large foreign macromolecules such as proteins and glycoproteins•Complex molecules make better antigens because they have more epitopes•Examples – components of bacterial cell walls, capsules, pili, flagella, viral proteins, fungal proteins, protozoal proteins, toxins, and some nucleic acid moleculesProperties and Types of AntigensB Lymphocytes (B Cells) and Antibodies•Found in the spleen, MALT, and primarily in the germinal centers of the lymph nodes–Small percentage of B cells circulate in the blood•Function in humoral immune responses and their major function is to secrete soluble antibodiesSpecificity of the B Cell Receptor (BCR)•Surface of each B cell is covered with 500,000 identical copies of the B cell receptor (BCR) which is a type of immunoglobulin•Each B cell randomly generates a single BCR during its development in the bone marrow•All the BCRs on a single B cell are the same, but the BCRs of one cell differ from the BCRs of all other B cells–Scientists estimate that each person forms from 10^9 to 10^13 B cells, each with its own BCR•When antigenic epitope stimulates a specific B cell via the unique BCR, B cell undergoes cell division, giving rise to nearly identical offspring that secrete immunoglobulins into blood or lymph–Immunoglobulins act against epitope that stimulated B cell•Activated, immunoglobulin-secreting B cells are called plasma cellsSpecificity of the B Cell Receptor (BCR)Specificity and Antibody Structure•Antibodies are free immunoglobulins and are similar to BCRs in shape•Secreted by activated B cells called plasma cells•Have identical antigen-binding sites and antigen specificity as the BCR of the activated B cellAntibody Function•Antigen-binding sites are complementary to epitopes–Antibody binding to epitope is the central functional