defense against disease Flashcards
Pathogens as the cause of infectious diseases
- Students should understand that a broad range of disease-causing organisms can infect humans.
- What are pathogens?
- What ways are pathogens spread?
- A disease-causing organism is known as a pathogen, although typically the term is reserved for viruses, bacteria, fungi and protists. Archaea are not known to cause any diseases in humans.
- body fluids, ingestion, direct contact, etc.
- Bacteria
- Viruses
- Fungi (think: mushrooms)
- Protozoan parasites
- Helminthic parasites
- prokaryote, can cause food poisioning/strep throat/pneumonia
- contains DNA/RNA, must attach to a host cell to reproduce, not considered cells, cause of flu, herpes, HIV
- eukaryotes, reproduce by producing spores, can cause athlete’s foot, ring worms, skin rashes
- Often parasitic or symbiotic organisms, Unicellular eukaryotes, making treatment difficult, can cause Malaria, Sleeping sickness, Lyme’s disease
- multicellular & eukaryote parasitic diseases, can cause elephantiasis
Differences between the innate immune system and the adaptive immune system
- Include the idea that the innate system responds to broad categories of pathogen and does not change during an organism’s life whereas the adaptive system responds in a specific way to particular pathogens and builds up a memory of pathogens encountered, so the immune response becomes more effective.
- Students are not required to know any components of the innate immune system other than phagocytes.
Innate:
- responds to a broad category of pathogens and does not change during an organism’s life
- 1st Line: skin secretions, saliva, stomach acid, mucus membrane with cilia in respiratory tract
- 2nd: phagocytes
Adaptive: (3rd)
- responds to specific pathogens in a particular way.
- builds a memory of encountered pathogens to improve the immune response against infection diseases
- involves lymphocytes
Skin and mucous membranes as a primary defence
- The skin acts as both a physical and chemical barrier to pathogens. Students are not required to draw or label diagrams of skin.
Skin
- acts as a physical barrier of entry for pathogens
- sebaceous glands associated with hair follicles release a fluid (sebum) that keeps skin moisturized and lowers pH
- reduced pH levels inhibits growth of bacteria and fungi
- natural microgranisms in skin live in competition for nutrients with harmful microorganisms
Mucus:
- cilia within mucus membranes traps pathogens which are swallowed or expelled by coughing
- mucus is a watery solution of glycoproteins, that contain anti-bacterial enzymes that can destroy pathogens
- has lubricating and protective function
Sealing of cuts in skin by blood clotting
- Include release of clotting factors from platelets and the subsequent cascade (sequence) pathway that results in rapid conversion of fibrinogen to fibrin by thrombin and trapping of erythrocytes to form a clot. No further details are required.
- what are clotting factors?
NOTE: clotting reduces blood lost, prevents fall in blood pressure, and pathogen invasion into blood stream
- Clotting factors are proteins in the blood that control bleeding and which are released by platelets. The clotting factors INITIATE a cascade of reactions
- each rxn in the cascade triggers the catalyst for the next rxn
Thrombin converts another soluble blood protein, fibrinogen, to insoluble fibrin fibres at the site of the cut.
- Within this mass of fibres, red blood cells are trapped and the blood clot has formed.
Infection control by phagocytes
- Include amoeboid movement from blood to sites of infection (shape change/move through cytoplasm), where phagocytes recognize pathogens, engulf them by endocytosis, and digest them using enzymes from lysosomes.
- phagocytes recognize pathogens, engulf them by endocytosis, and digest them using enzymes from lysosomes.
- Macrophages are specialized phagocytes that engulf foreign bodies, such as extracellular pathogens
- Different phagocyte cells work in different locations: neutrophils circulate in the blood, while macrophages are found in lymph, tissue fluid, lungs and other spaces, where they kill microbes before they enter the blood.
Lymphocytes as cells in the adaptive immune system that cooperate to produce antibodies
- antigens = foreign substances, antibodies correspond to a specific antigen & binds with it to neutralize antigen
- what are cytotoxic t-cells? helper t-cells? b-plasma cells? b-memory cells?
- Students should understand that lymphocytes circulate in the blood and are contained in lymph nodes.
They should appreciate that an individual has a very large number of B-lymphocytes that each make a specific type of antibody.
- They circulate in the blood and are contained in lymph nodes, which are part of the lymphatic system.
- T-cells are produced in bone marrow, processed in the thymus gland, often found in lymph nodes of the lymphatic system. Can differentiate into Helper T-cells or Cytotoxic T-cells.
- B-cells are produced in bone marrow, synthesize antibodies and can differentiate into antibody releasing B-Plasma cells or B-memory cells, once activated by T-cells.
- T-Lymphocytes communicate with other leucocytes, including B-lymphocytes, to signal the presence of a specific antigen. In response to this cooperation, B-cells mature into clones of plasma B-cells which secrete antibodies as well as long lived memory B-cells with antibody receptors specific to the antigen.
Antigens as recognition molecules that trigger antibody production
- Students should appreciate that most antigens are glycoproteins or other proteins and that they are usually located on the outer surfaces of pathogens. Antigens on the surface of erythrocytes may stimulate antibody production if transfused into a person with a different blood group.
antibodies can be in bloodstream/on cell membrane surface of B cells
- Antigens are proteins or glycoproteins on the cell membranes of pathogens which cells of the immune system recognize as foreign or “non-self”.
- An antibody is a globular protein with specific binding sites to an antigen. They are produced by B-lymphocytes and plasma cells in response to antigen recognition.
- The antigen binding site at the top of each arm gives each antibody its specifity, allowing it to bind to millions of different antigens.
NOTE: 5 actions of antibodies
Agglutination
Opsonization
Neutralization
Antibody-dependent cytotoxicity
Activation of complement
Activation of B-lymphocytes by helper T-lymphocytes
- Students should understand that there are antigen-specific B-cells and helper T-cells.
B-cells produce antibodies and become memory cells only when they have been activated. Activation requires both direct interaction with the specific antigen and contact with a helper T-cell that has also become activated by the same type of antigen.
- cell differentiation is also stimulated by…
NOTE: These protein complexes help cells of the immune system to identify each other.
For B lymphocytes to become antibody producing cells the presentation of antigens on an antigen presenting cell (e.g. phagocyte) is required.
The antigens are displayed to T-Helper cells on specific receptors (MHC), and the recognition is followed by an activation of killer T-Cells and B-lymphocytes.
chemical messenger molecules called cytokines and interleukins are used to stimulate cell differentiation
Multiplication of activated B-lymphocytes to form clones of antibody-secreting plasma cells
- There are relatively small numbers of B-cells that respond to a specific antigen. To produce sufficient quantities of antibody, activated B-cells first divide by mitosis to produce large numbers of plasma B-cells that are capable of producing the same type of antibody.
Each B cell is programmed to make one specific antibody. When a B cell encounters its specific or eliciting antigen it first changes into clones of plasma cells all carrying the same antigen receptor, which then further produce antibodies.
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