BIOL 222 Immune System Week 6
BIOL 222 Immune System Week 6 BIOL 222
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This 6 page Class Notes was uploaded by tanae tabron on Tuesday August 30, 2016. The Class Notes belongs to BIOL 222 at Towson University taught by Laura A. Martin in Spring 2015. Since its upload, it has received 4 views. For similar materials see Anatomy & Physiology II in Biology at Towson University.
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Date Created: 08/30/16
Immune System Danger to Our Bodies 1. Pathogens – Can have many different antigens. Disease- Causing organisms such as, bacteria, viruses, fungi. 2. Toxic chemicals/irradiation – Environment. Non-living threats to our health. May activate some of the same defense mechanisms. 3. Antigens – pathogen or part of pathogen or product of pathogen – can activate the immune system. Generate a defense against that part. Capable of stimulating immune response, that structure that’s capable of stimulate you can develop an antibody that is only for that specific piece. Formed Elements of Blood 1. 7 types of formed elements. Erythrocytes: Red blood cells (RBCs) Leukocytes: White blood cells (WBCs) Five leukocyte types divided into two categories Granulocytes (with dye – absorbing granules) Neutrophils – neither acidic or basic Eosinophils – acidic dye Basophils – basic dye Granulocytes (without granules) Monocytes Lymphocytes – different precursor (lymphoid stem cell) Platelets: cell fragments Form and Function White Blood Cell Characteristics 1. Conspicuous nucleus, contains organelles 2. Capable of amoeboid movement 3. Can migrate out of bloodstream (diapedesis) 4. Sensitive to chemical stimuli (chemotaxis) 5. Engulf pathogens or other foreign material (phagocytosis) Granulocytes 1. Neutrophils – (60% to 70%) – most abundant – “first response” 2. Eosinophils – (2% to 4%) – increased numbers in parasitic infections, collagen, diseases, allergies, disease of spleen and central nervous system (CNS). 3. Basophils – (less than 1%) role in inflammation, not phagocytic Secrete histamine (vasodilator) Secrete heparin (anticoagulant) Agranulocytes 1. Monocytes – (3% to 8%) Leave bloodstream and transform into macrophages 2. Lymphocytes – (25% to 33%) – increased numbers in diverse infections and immune responses. Protecting the Body: Lines of Defense 1. Non-specific resistance – guards equally against broad range of pathogens Effectiveness not dependent on prior exposure Neutrophils and macrophages, antimicrobial proteins, immune surveillance, inflammation, and fever External barriers, skin, mucous, hair, sweats, etc. 2. Specific resistance (aka adaptive immunity) – provides specific resistance against one particular pathogen. Either: Genetically programmed Results from prior exposure to pathogen Innate Defenses 1. Complement – works with antibodies; mark cells for destruction Kills the cell: recognize antibodies and destroys cells 2. Inflammation – increase blood flow: most cells, form of basophils Heparin Histamine Leukocytes and Macrophages – Non-specific 1. Neutrophils – circulate and wander into connective tissue killing bacteria – 2 mechanisms: Phagocytes and digestion – engulfing pathogens Produce a cloud of bactericidal chemicals by degranulation of lysosomes. Lysosomes discharge enzymes into extracellular fluid (ECF) to create a killing zone These enzymes catalyze the respiratory burst: neutrophil uses oxygen to produce toxic chemicals; kills neutrophil and bacteria Kill more bacteria with toxic chemicals than phagocytosis 2. Eosinophils – (2% to 4%) – increased numbers in parasitic infections, collagen diseases, allergies, diseases of spleen and CNS Phagocytize antigen – antibody complexes, allergens, and inflammatory chemicals Release enzymes to destroy large parasites 3. Basophils – (less than 1%) – increased numbers in chicken pox, sinusitis, diabetes – role in inflammation, not phagocytic Secrete histamine (vasodilator): speeds blood flow to an injured area Secrete heparin (anticoagulant): promotes mobility of other WBCs in the area 4. Monocytes (3% to 8%) – increased numbers in viral infections and inflammation Leave bloodstream and transform into macrophages Phagocytize pathogens and debris “present” antigens to activate other immune cells – antigen – presenting cells (APCs) Immune Surveillance 1. Natural Killer (NK) cells (type of lymphocyte) – seeks any abnormal antigens (non-specific) Bacteria, cells of transplanted organs, virus – infected cells, and cancer cells Recognize enemy cell NK cells bind to it Release proteins called perforins – create a hole in its plasma membrane of enemy cell Secrete protein – degrading enzymes – granzymes Enter via pore and degrade cellular enzymes and induce apoptosis of enemy cell Complement System – Works with Antibodies 1. Phagocytosis Complement assists neutrophils and macrophages by opsonization Coats microbial cells and serves as binding sites for phagocyte attachment – “prickle ball” less slippery 2. Cytolysis Complement binds to enemy cell (pathogen) Attracts more complement proteins – membrane attack complex forms Forms hole in target cell to destroy Fever – Abnormal Elevation of Body Temperature 1. Caused by pyrogens (fever producing agents from pathogen or from activated macrophages) that cause hypothalamus to reset body temperature to higher temperature Elevates metabolic rate and accelerates tissue repair Inhibits reproduction of bacteria and viruses Resets to lower (normal) temperature when danger has passed General Aspects of Specific Immunity 1. Immune system – population of cells that recognize specific foreign substances and act to neutralize or destroy them 2. Characteristics distinguish of specific immunity Specificity: immunity against a particular pathogen (antigen) Memory: when re-exposed to same pathogen, body reacts more quickly 3. Tolerance – recognizes self: doesn’t make cells to attack own cells Versality 4. Adaptive (Specific) Immunity – make a defense against different antigens Active immunity – your body makes immune defense Naturally acquired active immunity (got sick) – makes antibodies and cells Artificially induced active immunity – develops after administration of an antigen to prevent disease (vaccine). Innate (Non-specific) immunity – genetically determined, born with or develop very soon after birth Passive immunity – you are given the immune defense Naturally acquired passive immunity – conferred by transfer of maternal antibodies across placenta or breast milk. Artificially induced passive immunity – conferred by administration of antibodies to combat infection (rabies). Lymphocytes 1. Another type of WBC – produced from lymphoid stem cell 2. 3 types - % found circulating in bloodstream 80% T cells Tc/cytotoxic (kill cells/destroy pathogens) Th (helper) 15% B cells 5% NK cells – non-specific defense 3. Specific immunity – directed against specific pathogens B cells – humoral immunity B cells produce antibodies that mark cells for destruction T cells – cell mediates immunity T cells directly attack and destroy pathogens and infected 4. Antigen (ag) – molecule that triggers immune response; only attack non- self-antigens Can be part of a plasm membrane or bacterial cell wall or part of virus Can be toxin or venom 5. Epitope – aka antigenic determinant Portion of antigen that can trigger immune response Can have several epitopes on same antigen We can make antibodies (Ab) to each antigen, so attack can be more effective 6. T Lymphocytes (T cells) “Born” in red bone marrow Released into blood as undifferentiated stem cells that invade the thymus “maturation” in thymus – stimulates them to produce cell surface receptors to respond to only one antigen Becomes immunocompetent when they have antigen receptors Tested to be certain that it doesn’t attack self – needs to “self – tolerance” Those that pass the test undergo mitosis to make clones of identical T cells 7. “Deployment” of T cells that passed the test to lymphatic organs (spleen, bone marrow, lymph nodes, tonsils) to form colonies B lymphocytes (B cells) 1. Site of development Produced in the red bone marrow Stimulated to respond to single antigen, develop antigen receptors on surface that look like antibodies Form clones of identical B cells, respond to one antigen only 2. Migrate and colonize lymphatic organs, along with T cells When exposed to that antigen and activated, B cells will become plasma cells that produce antibodies that are released into the bloodstream Cellular Immunity 1. Cellular (cell – mediated) immunity – Tc T lymphocytes directly attack and destroy diseased or foreign cells 2. Cytotoxic T (Tc) cells – killer T cells (T8, CD8, or CD8+) Carry out attack on enemy cells 3. Helper T (Th) cells (T4, CD4, CD4+) Promote Tc cell and B cell action and nonspecific resistance 4. Memory T (Tm) cells Responsible for memory in cellular immunity – reserves Antigen Presentation 1. Antigens need to be “presented” on major histocompatibility complex (MHC) proteins for T cells to recognize them Infected cells with nuclei (no RBC) can stimulate the immune system by presenting Ag on MHC l proteins Antigens can be engulfed by APCs and can stimulate the immune system by presenting Ag on MHC ll proteins Antigen Processing and Presentation 1. Antigen processing in infected cells with nuclei Lysosomes digest pathogen into fragments (epitopes) MHC l Proteins are constantly being shuttled to and from cell membrane May contain normal cytoplasmic proteins (if normal) or antigenic fragments if infected Normal cell stuff ignored by T cells, but antigenic fragments stimulate immune system