Defence Against Infectious Diseases

Defence Against Infectious Diseases Immune System Define pathogen Pathogens are disease-causing agents (e.g. microorganisms, viruses and prions) ………………………………………………………………………………………………………………………………………………….......... Distinguish between bactericidal and bacteriostatic drugs Bactericidal drugs kill the invading bacteria whereas bacteriostatic drugs suppress its potential to reproduce ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... Outline how Florey and Chain demonstrated the antibiotic properties of penicillin The use of penicillin as a viable antibiotic was shown by Florey & Chain (1940) ………………………………………………………………………………………………………………………………………………….......... Mice injected with a pathogen (streptococcus), while half the mice were also injected with penicillin ………………………………………………………………………………………………………………………………………………….......... Untreated mice died from bacterial infection, whereas mice treated with penicillin survived ………………………………………………………………………………………………………………………………………………….......... Explain why antibiotics are effective against bacteria but not viruses Antibiotics are compounds that inhibit or kill bacteria by targeting the structures or metabolic pathways ………………………………………………………………………………………………………………………………………………….......... of prokaryotes (not eukaryotes) - viruses don’t have metabolism and so are not affected by antibiotics ………………………………………………………………………………………………………………………………………………….......... List five types of white blood cells Neutrophils - rapid response to microbial infections ………………………………………………………………………………………………………………… Lymphocytes - specific (adaptive) immune response ………………………………………………………………………………………………………………… Monocytes / Macrophages - longer lasting response to microbial infections ………………………………………………………………………………………………………………… Eosinophils - target multicellular parasites (too big to phagocytose) ………………………………………………………………………………………………………………… Basophils - involved in inflammation (similar to mast cells) ………………………………………………………………………………………………………………… Describe the function and organisation of the lymphatic system The lymphatic system is a transport system that protects the body by producing and filtering lymph ………………………………………………………………………………………………………………………………………………….......... Lymph contains white blood cells and arises from the drainage of fluid from blood and tissues ………………………………………………………………………………………………………………………………………………….......... Lymph is filtered at lymph nodes, where pathogens are removed before fluid is returned to venous circulation ………………………………………………………………………………………………………………………………………………….......... Major lymphatic organs include the spleen, tonsils, thymus and adenoids ………………………………………………………………………………………………………………………………………………….......... First Line of Defence Outline the role of surface barriers in the physical protection against infection Skin protects external structures and is a thick and dry region composed predominantly of dead cells ………………………………………………………………………………………………………………………………………………….......... Mucous membranes protects internal cavities and is a thin region composed of living cells that secrete mucus ………………………………………………………………………………………………………………………………………………….......... Sebaceous glands secrete biochemical agents / acids to inhibit bacterial growth ………………………………………………………………………………………………………………………………………………….......... Commensals (gut bacteria) prevent the colonisation of harmful pathogens in the digestive tract ………………………………………………………………………………………………………………………………………………….......... Describe, with the aid of the diagram, the process of clotting Injured cells and platelets release clotting factors ………………………………………………………………………………………… Factors convert prothrombin (inactive) into thrombin (active) ………………………………………………………………………………………… Thrombin converts fibrinogen (soluble) into fibrin (insoluble) ………………………………………………………………………………………… Fibrin forms a mesh of insoluble fibres that trap blood cells ………………………………………………………………………………………… Clotting factors also cause platelets to become sticky and ………………………………………………………………………………………… form a solid plug (clot) ………………………………………………………………………………………… ………………………………………………………………………………………… Describe the causes and consequences of clotting in the coronary arteries Blood clots form in coronary arteries when the vessels are damaged by cholesterol build-up (atherosclerosis) ………………………………………………………………………………………………………………………………………………….......... The restricted blood flow increases pressure in the artery, leading to damage to the arterial wall (plaques) ………………………………………………………………………………………………………………………………………………….......... If the plaque ruptures, blood clotting is triggered, forming a thrombus that restricts blood flow ………………………………………………………………………………………………………………………………………………….......... Clot formation in coronary arteries leads to coronary thrombosis and heart attacks ………………………………………………………………………………………………………………………………………………….......... Second Line of Defence Identify five non-specific defence mechanisms the body uses to combat infection Phagocytosis - pathogens are engulfed and destroyed by phagocytic leukocytes 1. …………………………………………………………………………………………………………………………………………………... Inflammation - blood flow is increased to site of infection to increase leukocyte access 2. …………………………………………………………………………………………………………………………………………………... Complement proteins - activate a cascade that promotes pathogen detection and destruction 3. …………………………………………………………………………………………………………………………………………………... Fever - increases body temperature to assist in pathogenic destruction 4. …………………………………………………………………………………………………………………………………………………... Natural killer cells - non-specifically target viral-infected cells 5. …………………………………………………………………………………………………………………………………………………... Outline the process and purpose of inflammation When tissue damage occurs, mast cells and basophils release histamine which causes local vasodilation and ………………………………………………………………………………………………………………………………………………….......... increases capillary permeability to improve the recruitment of leukocytes to the region ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... Outline how phagocytic leukocytes ingest and present pathogens in the blood and body tissues Phagocytes (macrophages) circulate in blood but move to tissue upon infection …………………………………………………………………………………………………………… Pathogens are engulfed by the phagocyte and internalised in a vesicle …………………………………………………………………………………………………………… The vesicle may then fuse with the lysosome to digest the pathogen …………………………………………………………………………………………………………… Antigenic fragments from the pathogen are presented on the macrophage …………………………………………………………………………………………………………… These fragments are then presented to lymphocytes in order to help stimulate …………………………………………………………………………………………………………… the production of specific antibodies …………………………………………………………………………………………………………… Third Line of Defence Identify the two key properties of the adaptive immune system Adaptive: It can differentiate between pathogens and target a response that is specific to a given pathogen ………………………………………………………………………………………………………………………………………………….......... Memory: It can respond rapidly upon re-exposure to a specific pathogen, preventing disease symptoms ………………………………………………………………………………………………………………………………………………….......... Distinguish between antigens and antibodies Antigens are molecules that are capable of inducing an immune response Antigen: ………………………………………………………………………………………………………………………………………….. Antibodies are proteins produced by lymphocytes that recognise and neutralise specific antigens Antibody: ……………………………………………………………………………………………………………………………………….. Label the structure of an antibody Variable region (antigen binding site / epitope) 1. ………………………………………………………………………… Light chain 2. ………………………………………………………………………… Heavy Chain 3. ………………………………………………………………………… What is the alternative name for an antibody? Immunoglobulin ……………………………………………………………………………… ……………………………………………………………………………… Explain antibody production (humoral immunity) The antigenic fragments of pathogens are presented on the macrophages ………………………………………………………………………………………………………………………………………………….......... Lymphocytes are a class of white blood cells that develop in the bone marrow ………………………………………………………………………………………………………………………………………………….......... Macrophages present antigen fragments to helper T lymphocytes (TH cells) ………………………………………………………………………………………………………………………………………………….......... TH cells release cytokines to activate an antigen-specific B lymphocyte (B cell) ………………………………………………………………………………………………………………………………………………….......... The B cell divides and differentiates into plasma cells that produce antibodies ………………………………………………………………………………………………………………………………………………….......... A small proportion of clones develop into memory cells (for long-term immunity) ………………………………………………………………………………………………………………………………………………….......... Immune System Disorders Identify three types of immune system disorders Hypersensitivity disorders (i.e. allergic reactions) 1. …………………………………………………………………………………………………………………………………………………... Autoimmune disorders (e.g. multiple sclerosis, lupus) 2. …………………………………………………………………………………………………………………………………………………... Immunodeficiency disorders (e.g. HIV / AIDS) 3. …………………………………………………………………………………………………………………………………………………... Describe the effects of HIV on the immune system The human immunodeficiency virus (HIV) is a retrovirus that infects helper T cells ………………………………………………………………………………………………………………………………………………….......... HIV is integrated into the genome of the helper T cells and after years of inactivity the virus spreads ………………………………………………………………………………………………………………………………………………….......... Infected TH cells are lysed (destroyed) in order to release the virus from the cells ………………………………………………………………………………………………………………………………………………….......... This results in reduced immunity (AIDS) as antibody production is compromised ………………………………………………………………………………………………………………………………………………….......... Define allergen An environmental substance that triggers an immune response despite not being intrinsically harmful ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... Describe the role of histamine in the allergic response When a B cell encounters the allergen, it differentiates into plasma cells and makes a specific antibody (IgE) ………………………………………………………………………………………………………………………………………………….......... The IgE antibodies attach to mast cells, effectively ‘priming’ them towards the allergen ………………………………………………………………………………………………………………………………………………….......... Upon re-exposure, the IgE-primed mast cells release large amounts of histamine which causes inflammation ………………………………………………………………………………………………………………………………………………….......... …………………………………………………………………………………………………………………………………………………..........