Defense Against Infectious Disease Flashcards
Know what a pathogen is.
A pathogen is a “disease-causing agent” (bacteria, protists, fungi, parasites, viruses, and prions) that disrupts the normal physiology of an organism.
Know what antibiotics are and be able to explain why they are effective against bacteria but NOT viruses.
Antibiotics are compounds that kill or inhibit pathogenic growth by targeting prokaryotic features. But they don’t harm eukaryotic cells (i.e. don’t affect the host organism). They are effective against bacteria because bacteria contain prokaryotic cell structures and pathways. But they aren’t effective against viruses because viruses aren’t prokaryotic, so antibiotics have nothing to target.
Be able to explain how skin and mucous membranes are effective (non-specific) barriers against pathogens.
Skin:
- Protects external structures
- The epidermis is thick, dry, and composed of predominantly dead skin cells that can be “shed” after 2 weeks, carrying with them any microbes lying on the outermost surface of our skin. This includes any harmful pathogens trying to break through the skin barrier into the body.
- Consists of glands (ex: sweat glands) that secrete chemicals to inhibit bacterial growth.
Mucous Membrane:
- Protects internal structures and cavities
- Thin region composed of living cells that secrete mucous to trap pathogens/invading microbes, limiting and preventing them from infecting the body’s cells.
Know the process of blood clotting and the roles of the proteins involved in this process.
• Injured cells and platelets release clotting factors. As blood circulates, more platelets are brought to the damaged area and they “stick” together to form a “primary plug.”
• These factors convert prothrombin into thrombin
• Thrombin rapidly converts fibrinogen (soluble) into fibrin (insoluble)
• Fibrin forms a mesh of fibres that block the injured site
• Clotting factors also cause platelets to become sticky and
form a solid plug (called a clot), sealing the wound
• This process of events is called a coagulation cascade
Be able to explain the role of wandering macrophages (phagocytic leukocytes) in defending against pathogens (non-specific).
“Wandering” macrophages (phagocytic leukocytes) are non-specific defenses that target ALL foreign invaders. They are able to change their shape and move in and out of blood vessels/tissue to “look” for foreign invaders. When a macrophage “meets” a cell, it will determine whether or not the cell is “self” or “non-self” based on the surface proteins of present in the cell’s membranes (self = MHCs, non-self = antigens). If a cell is “non-self,” the macrophage will change shape to engulf it (phagocytosis) and enzymes (lysosomes) within the macrophage will chemically digest it - destroying it.
Know the difference between an antigen and an antibody (immunoglobulin).
Antigens are foreign surface proteins that identify a microbe as “non-self” to the body, allowing the macrophage to engulf the microbe and partially digest it (non-specific immune response).
Antibodies are proteins that are produced by specialized plasma cells/white blood cells that are produced in response to specific antigens (specific immune response).
Know HOW antibodies work/ defend your body against pathogens (and know that they are produced by plasma cells - which are produced by B lymphocyte cells during clonal selection/ B cell cloning).
Antibodies are produced by plasma cells, which are produced by B-lymphocyte cells during clonal selection/B cell cloning. They are Y-shaped proteins that are EXTREMELY specific - they bind (complementary (like a key to a lock)) to specific antigens and act as “tags” on pathogen surfaces. “Tags” cause pathogens to agglutinate or they trigger white blood cells in the immune system to attack and destroy foreign and/or infected cells (opsonization).
Be able to explain the steps of antibody production in the body (beginning with macrophages, and including the lymphocytes helper T cells, B cells, plasma cells, and memory cells).
In a PRIMARY INFECTION (first exposure to a pathogen), Wandering Macrophages identify “non-self” antigens and engulf/ingest pathogens. Antigens (or pieces of them) from the pathogen remain in the macrophage and are “presented” on the macrophage cell membrane to WBC’s called helper-T cells - this activates the helper-T cells.
Helper-T cells release cytokines to activate specific B cells (lymphocytes - produced in bone marrow - millions of different types) in the body that are able to produce the specific antibody that is needed for that specific pathogen.
Because B cells exist in VERY SMALL NUMBERS in the bloodstream, they begin to rapidly divide (mitosis) once they are activated. This is so that there are enough of them to produce a specific antibody in large enough amounts to be effective (B cell cloning/clonal selection).
B cell cloning produces two types of cells: Antibody-secreting plasma cells (to make secrete antibodies to “target” the primary infection for destruction) and memory cells (long-lived cells that remain in the bloodstream to secrete antibodies if a subsequent infection of the same pathogen occurs, granting your body immunity).
Be able to distinguish between innate and acquired immunity.
Innate immunity means that it is genetic (you are born with that immunity) whilst acquired immunity means that you develop it over time.
Be able to distinguish between passive and active immunity.
Active immunity: The immune system is “challenged” by an antigen (naturally or artificially), responds, and produces memory-cells, leading to long-term immunity (an individual organism produces its own antibodies).
Passive immunity: One organism receives antibodies from another organism/source. This confers SHORT-TERM benefit only (antibodies target antigens and pathogens are destroyed). NO memory cells are produced in the organism who receives the antibodies though (no long-term immunity).
Be able to distinguish between natural and artificial immunity.
Natural immunity: An organism is naturally exposed to an infectious agent.
- If the organism is an infant, they receive maternal antibodies (acquired immunity).
Artificial immunity: An organism is purposefully and (often) medically exposed to an infectious agent to provide immunity against that pathogen.
Know what a vaccine (aka immunization) is and how it works to provide immunity to your body.
Vaccine/immunization is a form of artificial immunity. Vaccines contain antigens to trigger immunity but do not cause disease.
They are developed by “weakening” a pathogen and and injecting it (or parts of it) into the body to PURPOSEFULLY TRIGGER A PRIMARY IMMUNE RESPONSE. The body recognizes the weakened pathogen as “non-self” and begins the process of a primary immune response, which will eventually result in memory B cell formation (long-term immunity).
Know what monoclonal antibodies are.
Monoclonal antibodies are all of the same antibodies that are produced that are the EXACT SAME.
How are monoclonal antibodies produced?
A particular antigen is injected into a lab animal (usually a mouse). A primary immune response is allowed to occur in the animal (polyclonal). The animal’s spleen is harvested (via blood cells). Lymphocytes/B cells are identified, isolated, removed, and grown with cancerous cells (myeloma - divide forever).
Some of the B cells (which produce antibodies) fuse with the myelomas as they grow together, forming hybridomas. Individual hybridomas are identified and grown in their own SEPARATE containers. An ELISA (enzyme-linked immunosorbent assay) test is used to identify which hybridoma cultures are producing the ONE desired antibody. The cells in these cultures continue to divide (mitosis) and produce a large amount of the ONE (monoclonal) desired antibody (which can be purified and used to treat or diagnose patients)
What are monoclonal antibodies used for?
Monoclonal antibodies are used to help detect and/or diagnose disease, as HCGs in pregnancy tests, and as treatment for cancerous patients or patients who have been bitten by a venomous or rabid animal.
