BIOL 202 Lecture 10: Chapter 20: Innate Immunity
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Department
Biological Science
Course
BIOL 202
Professor
Cathie Overstreet
Semester
Spring

Description
Chapter 20: Resistance and the Immune System Innate Immunity • Innate immunity is obtained by birth. • Metchnikoff (1908) directly observed the activity of the immune system in a clear-colored starfish. o Doctrine of phagocytosis: a body responds to pathogens through the release of macrophages at site of pathogen to initiate phagocytosis. o Macrophages take the material that they engulf, chop it up, and display it on the surface. ▪ This material enters the lymph nodes and the lymph nodes search for a b-cell or t-cell that match against that material; that particular b/t cell is then activated. Host Immune Defenses • Immunology: study of how immune system functions to prevent infection. • Innate immunity: immediate response. o Effector molecules (molecules present at birth); present in skin, mucus, membranes, and secretions (tears, etc). o Innate immunity keeps infection in check while cytokines are sent in order to initiate adaptive immunity. • Adaptive immunity: slow response. o Takes about a week since it requires activation and antibody production. o Highly specific to a particular pathogen. o Antibodies are present for life. Host Immune Defenses • Blood consists of: o Fluid ▪ Serum: cell free part of blood. ▪ Water, minerals, salt, proteins, antibodies, hormones. o Plasma ▪ Serum that contains clotting agents. o Blood and immune cells ▪ Platelets ▪ RBC (erythrocytes) ▪ WBC (leukocytes) Leukocytes • Neutrophils (phagocytes): o Contain digestive enzymes and antimicrobial agents that can kill pathogens. • Eosinophils: contain toxic compounds to defend against parasites. • Basophils: act in allergic reactions. • Monocytes: o Last only a couple weeks but mature into macrophages. • Lymphocytes: o Natural killer cells; destroys virus infected and abnormal cells. ▪ Kills cancer cells. • Dendritic Cells o Present in every portal of entry. Lymphatic System • Cells and Tissues Essential to Immune Function • Thymus ensures that T/B-cell does not target the body (self-molecule). o After being ‘educated’ by the thymus, these cells enter the lymph nodes. • Lymph nodes: o This is where B/T -cells are located. o Dendritic cells and macrophages display what they have captured to the B/T-cells (recall—these are antigen presenting cells). 2 ▪ Cortex: B-cells. ▪ Medulla: T-cells. Invaders: Pathogen Identification • Recognition Phase o Body’s immune cells need to distinguish normal body cells from the invader. o Identify self-molecule from non self-molecule. ▪ Pathogens have flagella, peptidoglycan, lipopolysaccharides, etc… while the body’s cells do not. • Activation Phase o Neutrophils, macrophages, dendritic cells are put in action as the first responders. ▪ Neutrophils come first; monocytes turn to macrophages; dendritic cells come last. • Effector Phase o Notification: signaling molecules are sent by effector cells in order to alert more cells (phagocytic) to the site of pathogenic infection. ▪ Cytokine: a molecule secreted from cells (DC, macrophages, T-cells) that communicates to other phagocytic cells to the site. • Interleukin: cytokines that are involved in the communication between leukocytes; bind to cytokine receptors on target cells. • Chemokines: trigger attraction of leukocytes. o Create a chemical gradient to attract cells to that site. Adaptive Immunity • Has to acquire information from whatever has been infecting the body. o This requires the presence of antigen presenting cells. • We have billions of T-cells and millions of b-cells. 3 o However, it takes long to create antibodies since the T/B-cells need to be educated. Interleukins Between Leukocytes • A macrophage has to trigger a specific response to a pathogen it has found. Suppressor of Cytokine Signaling (SOCS) • At some point, a cytokine storm is possible in which there are too many white blood cells in an area; can be deadly. • There is a gene pro
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