Transcript Immunity
Immunity Protection /defense . . . against whatever doesn’t belong Other pathogens Cancer Chemicals Damage/ injury Immunity The military model ^& police Two main strategies . . . Innate (nonspecific) immunity Adaptive (antigen-antibody) immunity Innate (Nonspecific) Defenses There are many innate strategies; here are a few • • • • Species resistance Lines of defense (as in military model) Surface barriers - skin and mucous membranes Phagocytes - neutrophils, eosinophils, macrophages WBCs (leukocytes) • The immune system is made up white blood cells, which are often fancily referred to as leukocytes or WBCs. There are five major types of white blood cells that make up the immune system: lymphocytes, monocytes (aka macrophages), basophils, neutrophils, and eosinophils. Phagocytes are a type of WBC • Monocytes are big and slow Pacman-like cells that eat other cells whole. It can take 3-5 days for these bad boys to arrive on the scene, and so the immune system has • Neutrophils, which are smaller and stealthier. • Basophils are basically wimps. • Eosinophils fight crime in the form of parasitic infections neutrophil Monocyte, tissue macrophage • A tissue macrophage is a mature phagocyte that can ingest and destroy invading microbes, foreign particles and cellular debris. • A monocyte is a circulating phagocyte that ingests microbes, invading particles, and cellular debris. • Monocytes leave the blood stream and usually mature into tissue macrophages. Tissue macrophages (pink/purple), T lymphocytes (green), and human red blood cells from a leg wound. Viruses and Bacteria • Which can adapt? • Which is worse to treat? Types of bacterial infections: strep, staph, Types of viruses: HIV, influenza, colds (rhinovirus), Defensive proteins (cytokines) • Interferons (IFNs) are released by dying, virus-infected lymphocyte or other cell • Interferons "call in" other immune cells (NK cells and macrophages) that destroy virus-infected cells, protecting the body from further spread of viral infection • Interferons also "interfere" with the ability of viruses to replicate in other nearby cells --also stopping the viral infection • Chemical attractants are released from damaged tissue cells and immune system cells to "call over" immune cells to the site of injury Inflammation (the inflammatory response) • Set of reactions in response to injury • Four principle signs of inflammation: redness, warmth, pain, swelling • Inflammation mediators are chemicals that regulate the inflammatory response • Fever Types of adaptive (specific) immunity WBC • Active – reaction of your own system • Passive Pathogen – borrow immune agents from another person Antibodies Types of adaptive immunity • Natural – occurs accidentally, on its own – Active – you are exposed to the flu, then develop immunity to that flu strain – Passive – a fetus receives antibodies from mom • Artificial – stimulated on purpose – Active – vaccination with a killed virus triggers immunity to the live virus – Passive – Injection of antibodies provides immunity Good to Know • Passive is temporary • Active is permanent (or semi-permanent) Inappropriate immunity • Autoimmunity – “self” cells are attacked (abnormal) • Allergy (Hyperimmunity) – excessive response to antigen, or response to something not normally an antigen (allergen) • Lymphocytes come in three flavors, B-cells, Tcells, and Natural Killer (NK) cells. – B-cells can become plasma cells and produce antibodies. – T-cells exist in 2 forms, helper T-cells and killer T-cells. • Helper T-cells are a bit like antibodies and help tag bacteria for destruction. • Killer T-cells and NK cells do exactly what it sounds like they do -- they kill bacteria. Natural killer (NK) cells • NK cells are lymphocytes that "patrol" the body, looking for abnormal cells (esp. cancer cells and virus-infected cells) to kill • NK cells kill by direct contact with enemy cell • Kill by various methods • Lymphocytes are involved in the specific immune response and are composed mainly of precursor T cells and B cells (pre-T and B cells). • Pre-T cells (also known as T lymphocytes) circulate in the blood before migrating to the thymus where they develop into specialized cells (helper T and killer T cells) that are able to identify antigens and infected tissue cells Effector and memory cells • Effector cells are the cells that actively participate in "the battle" against "the enemy" • Effector cells usually die during or just after the "battle" Memory cells are inactive copies of the effector cells that are held as "reserves" in case the same enemy attacks later • Memory T cells and memory B cells can quickly be activated or "called up to the front" and become effector cells if the same enemy attacks again at a later time