Biology of Humans: Chapter 13 - Body Defense Mechanisms

PLAN of antibodies

(Manners in which antibodies defense against pathogens in the body) - Precipitation: the antigen-antibody binding causes antigens to clump together and precipitate (settle out of a solution), enhancing phagocytosis by making the antigens easier for phagocytic cells to capture and engulf. - Lysis (bursting): certain antibodies activate the complement system, which then pokes holes through the membrane of the target cell and causes it to burst. - Attraction of phagocytes: antibodies also attract phagocytic cells to the area. Phagocytes then engulf and destroy the foreign material. - Neutralization: antibodies bind to toxins and viruses, neutralizing them and preventing them from causing harm.

Immwddiate

1) an immediate allergic response begins when a person is exposed to an allergen (antigen) - which enters the body - and a primary immune response is launched. 2) plasma cells produce large amounts of class IgE antibodies against the allergen, which binds to either basophils or mast cells. 3) In subsequent exposures to that allergen, the allergen binds to IgE antibodies on the surface of mast cells and cause histamine and other chemicals to be released from mast cell granules 4) Histamine causes blood vessels to widen and become leaky. Fluid enters the tissue, causing swelling, redness, and other symptoms of an allergic response - and the tissue swells 5) Histamine stimulates release of large amounts of mucus; nose runs. If the allergen moves from the area where it entered the body, these effects can become widespread and can result in anaphylactic shock. (254)

Defense - The Antibody-Mediated Response

1) activated B Cells divide and produce plasma cells through clonal selection 2) the plasma cells secrete antibodies into the bloodstream to defend against antigens free in the blood or bound to a cell surface 3) The antibodies recognize a specific antigen by its shape (each antibody specific for one particular antigen) 4) The antibodies help defend against these pathogens

2. Eosinophil (phagocyte)

A type of white blood cell that attacks pathogens that are too large to be consumed by phagocytosis, such as parasitic worms. Eosinophils get close to the parasite and discharge enzymes that destroy the organism. Macrophages then remove the debris (241).

Macrophage

A type of white blood cell that ingests foreign particles and infectious microorganisms by the process of phagocytosis. They attack and consume virtually anything that is not recognized as belonging in the body - including viruses, bacteria, and damaged tissue (241). They are like the scouts of the immune system (245). They alert helper T cells.

Monocyte

A type of white blood cell which leaves the vessels of the circulatory system and enters the tissue fluids, where it develops into large macrophages (241).

1. Neutrophil (phagocyte)

A type of white blood cell, which arrives at the site of attack before the other types of white blood cells and immediately begins to consume the pathogens, especially bacteria, by phagocytosis. (241)

cancerous cells

A, once normal, body cell that, because of changes in its genes, can no longer regulate its own division. "If left unchecked, these renegade cells can multiply until they take over the body, upsetting its balance, choking its pathways, and ultimately causing great pain and sometimes death" (239).

Fever

An abnormally high body temperature - caused by pyrogens - that occurs during infection and inflammation. It intensifies the effects of interferons, inhibits growth of bacteria, stimulates body defense responses, and speeds up body reactions that aid repair - helping the body in the fight against bacterial infections. A very high fever over 105 degrees Fahrenheit is dangerous. It can inactivate enzymes needed for biochemical reactions within body cells (243-244).

Allergies

The result of the immune system protecting us against substance that are not harmful (252). An allergy is an overreaction by the immune system to an antigen, in this case called an allergen, that usually is not harmful to the body (254). Most common allergy: hay fever/ allergic rhinitis (symptoms: sneezing, nasal congestion common causes: pollen, mold spores, animal dander, and the feces of dust mites) (254).

Autoimmune disorders

Disorders that occur when the immune system fails to distinguish between self and nonself and attacks the tissues or organs of the body. (252). A number of them occur because portions of disease-causing organisms resemble proteins found on normal body cells. If the immune system mistakes the body's antigens for the foreign antigens, it may attack them (253). The body's own cells are attacked I.e. Friendly fire (252). -Organ-specific autoimmune disorders: autoimmune disorders directed against a single organ. They are usually caused by T-Cells that have gone awry. (ex: Hashimoto's thyroiditis and Type 1 diabetes) - Non-organ-specific autoimmune disorders: autoimmune disorders generally caused by antibodies produced by B cells gone awry and tend to have effects throughout the body . (ex: Systemic lupus erythematosus) (253).

Monoclonal Antibodies

Groups of identical antibodies that bind to one specific antigen. -They are used in home-pregnancy tests to react to a hormone secreted by membranes associated with the developing embryo. - They have proved useful in screening for certain diseases, STD's, and cancers - They have been used in cancer treatment

Anaphylactic Shock

An extreme allergic reaction that occurs within minutes after exposure to the substance a person is allergic to. It can cause pooling of blood in capillaries, which leads to dizziness, nausea, and sometimes unconsciousness as well as extreme difficulty in breathing. While it can be fatal, most people survive Allergies that are common triggers of anaphylactic shock include: certain foods, medicines (including antibiotics such as penicillin), insect stings (especially from bees, wasps, yellow jacket and hornets). (255).

food allergy

An immune response to a particular food, occurring in the digestive system. It may cause nausea, vomiting, abdominal cramps, and diarrhea. Food allergies may also produce hives (a condition in which patches of skin temporarily become red and swollen) (254).

Lymphocytes

White blood cells that are responsible for both the specificity and the memory of the adaptive immune response. (245). Two types: (1) B lymphocytes (B cells): form in the bone marrow. Mature in the bone marrow. (2) T lymphocytes (T cells): form in the bone marrow, mature in the thymus gland. As they mature they develop the ability to distinguish cells that belong in the body from those that do not. Those cells which don't belong are destroyed by the T cells. (T Cells that fail to do their job properly, and attack cells with self-markers, are destroyed).

antibodies

Y-shaped proteins which neutralize and remove potential threats from the body. They are programed to recognize and bind to the antigen posing the threat; they help eliminate the antigen from the body (246).

helpful bacteria can

- flavor our cheese and produce food - help rid the planet of corpses through decomp - help keep potentially harmful bacteria in check within our bodies (239).

The Second Line of Defense - Innate, Nonspecific Internal Defense

1. Defensive Cells - Phagocytic cells, such as neutrophils and macrophages: Engulf invading organisms. - Eosinophils: Kill parasites. - Natural Killer cells: Kill many invading organisms and cancer cells. 2. Defensive Proteins - Interferons: Slow the spread of viruses in the body - Complement system: Stimulates histamine release, promotes phagocytosis, kills bacteria, enhances inflammation. 3. Inflammation - Widening of blood vessels and increased capillary permeability, leading to redness, heat, swelling and pain: Brings in defensive cells and speeds healing. 4. Fever - Abnormally high body temperature: Slows the growth of bacteria; speeds up body defenses (241).

Three Lines of defense against foreign organisms and molecules, or cancer cells

1. Keep the foreign organisms or molecules out of the body in the first place. This is accomplished by the first line of defense - chemical and physical surface barriers. 2. Attack any foreign organism or molecule or cancer cell inside the body. The second line of defense consists of internal cellular and chemical defenses that become active if the surface barriers are penetrated. 3. Destroy a specific type of foreign organism or molecule or cancer cell inside the body. The third line of defense is the adaptive immune response, which destroys specific targets (usually disease-causing organisms) and remembers those targets so that a quick response can be mounted it they enter the body again. (1st and 2nd line of defense, innate responses, are effective against any foreign organism or substance - we are born with them. 3rd line of defense, the immune response, is adaptive - we acquire it when we're exposed to foreign chemicals and organisms) (240).

Steps in the Adaptive immune response

1. Threat - (foreign cell enters body) 2. Detection - (macrophage detects and engulfs it) 3. Alert - (macrophage puts antigen from pathogen on its surface and finds proper helper T cell to alert it of the invader with that antigen, activating the T cell) 4. Alarm - (Helper T Cell activates both lines of defense to fight that specific antigen) 5. Building specific defenses - (antibody-mediated defense and cell-mediated defense) 6. Defense - (antibody and cell-mediated defense) 7. Continued surveillance - (memory cells formed) 8. Withdrawal of forces - (once antigen has been destroyed, suppressor t cells shut down the immune response to that antigen)

Active Immunity

A form of immunity that occurs naturally whenever a person gets an infection. In this type of immunity, the body actively defends itself by producing memory B cells and T cells following exposure to an antigen (251). Active immunity can also develop through vaccination (also known as immunization).

antigen

A nonself (foreign) substance or organism that triggers and immune response. Because it is not recognized as belonging in the body, it is labeled a foe, and the immune system directs an attack against it (245). Antigens can be: - large molecules (proteins, polysaccharides, nucleic acids) - found on the surface of invaders - pieces of invaders and chemical secreted by them (bacterial toxins) (245).

Vaccination (immunization)

A procedure that introduces a harmless form of an antigen into the body to stimulate adaptive immune responses against that antigen (251). Active immunity can be developed through vaccination, and is relatively long-lived. (The first dose of a vaccine causes the primary immune response, and antibodies and some memory cells are generated).

3. Natural Killer (NK) cell

A third type of white blood cell which roams the body in search of abnormal cells and quickly orchestrates their death. The prime targets of NK cells are cancerous cells and cells infected with viruses (241). - Cancerous cells routinely form but are quickly destroyed by NK cells and prevented from spreading (241-242).

Suppressor T Cells

A type of T lymphocyte that turns off the immune response, when the level of antigen falls (and the antigen no longer poses a threat), by releasing chemicals that dampen the activity of both B cells and T cells (250).

Effector Cells

Cells formed by the repeated division of B and T cells bearing receptors able to respond to a particular antigen that has been detected by the body. Effector cells carry out the attack on the enemy. They generally live for only a few days; after the invader has been eliminated from the body, the number of effector cells declines. (245).

Memory Cells

Cells produced by the repeated division of B and T cells bearing receptors able to respond to a particular antigen that has been detected by the body. Memory cells are long-lived cells that "remember" that particular invader and mount a rapid, intense response to if it should ever appear again. The quick response of memory cells is the mechanism that prevents you form getting ill from the same pathogen twice (245).

Classes of antibodies (immunoglobulins)

IgG: Enhances phagocytosis; neutralizes toxins; triggers complement system. IgA: Prevents pathogens from attaching to epithelial cells of surface lining. IgM: Powerful agglutinating agent (10 antigen-binding sites); activates complement IgE: Thought to be involved in recognition of antigen and in activating B cells. IgD: Involved in allergic reactions by triggering release of histamine and other chemicals from mast cells or basophils (250).

Second Line of Defense: Defensive Cells and Proteins, Inflammation, and Fever

Nonspecific internal defenses against any pathogen that breaks through the physical and chemical barriers and enters the body. The Second Line of Defense includes defensive cells and proteins, inflammation, and fever. - Defensive Cells: Cells that serve as the front-line soldiers in the body's internal defense system and the janitors that clean up the debris. (240).

primary response

Initial response (body's first encounter) to a specific antigen. Relatively slow. During a primary response, T and B lymphocytes are activated and specific antibodies and memory cells to the antigen produced. (250)

Cells Involved in the Adaptive Immune Response

Macrophages (dendritic cells or B Cells), T Cells (Helper T cells), Cytotoxic T Cells (effector T cells), Suppressor T cells, B Cells, Plasma Cells, Memory Cells (246).

MHC (Major histocompatibility complex) Markers

Markers (molecules) embedded in the plasma membranes of the cells in your body that label that cell as "self," distinguishing it from foreign organisms or molecules. The body doesn't attack cells that are recognized as self (245).

Epinephrine auto-injectors (Epi-Pens)

Prescribed by doctors, for people with extreme allergies. These devices automatically administer the correct dose of epinephrine to stop an allergic response. The epinephrine constricts blood vessels and keeps blood pressure from dropping dangerously low.

Passive Immunity

Protection that results when a person receives antibodies produced by another person or animal. The effects of passive immunity are immediate, but protection is short-lived. The borrowed antibodies circulate for 3 to 5 weeks before being destroyed in the recipient's body. Protection disappears with the antibodies. For instance, some antibodies produced by a pregnant woman can cross the placenta and give the growing fetus some immunity. Breast milk also contains antibodies that provide passive immunity to nursing infants(252)

2. The Complement system (Defensive proteins)

Proteins which assist other defensive mechanisms. A group of at least 20 proteins whose activities enhance, or complement, the body's other defense mechanisms. Until activated, they circulate the blood in an inactive state. Once activated complement proteins: - Destroy pathogens by: 1) punching holes in a target cell's membrane, so that 2) the cell is no longer able to maintain a constant internal environment and 3) water enters the cell and causes it to burst - Enhance phagocytosis by: 1) attracting macrophages and neutrophils to the site of infection to remove the foreign cells 2) one of the complement proteins binding to the surface of the microbe, making it easier for the macrophages and neutrophils to catch and devour the microbe. -Stimulate inflammation by: ~ Causing blood vessels to widen and become more permeable - providing increased blood flow to the area and increased access for white blood cells. (242).

clonal selection

The process by which an antigen selectively binds to and activates only those lymphocytes bearing receptors specific for the antigen. The selected lymphocytes proliferate and differentiate into a clone of effector cells and a clone of memory cells specific for the stimulating antigen.

1. Interferons (Defensive proteins)

Small proteins, secreted by certain virally infected cells before they die, which act to slow viral reproduction. Virally infected cells can help cells, that have not yet been infected by that virus, by interfering with viral activity through the secretion of interferons prior to their deaths. (242) They: 1) help rid the body of virus-infected cells by attracting macrophages and NK cells that destroy the infected cells immediately 2) warn cells that are not yet infected with the virus to take protective action, helping protect uninfected cells from ALL strains of viruses, not just the one responsible for the initial infection (242).

Allergy treatment (desensitization)

Some allergies can be treated by gradually desensitizing the person to the offending allergens. Allergy shots containing gradually increasing amounts of a known allergen are injected into the person's bloodstream. The allergen causes the production of IgG antibodies, which will bind to the allergen the next time it enters the body, and prevent it from binding to IgE antibodies on mast cells and triggering an allergic reaction (255).

Phagocyte (defensive cell)

Specialized scavenger cells that engulf pathogens, damaged tissue, or dead cells by the process of phagocytosis. When a phagocyte encounters a foreign particle, cytoplasmic extensions flow from the phagocytic cell, bind to the particle, and pull it inside the cell. Once inside the cell, the particle is enclosed within a membrane-bound vesicle and quickly destroyed by digestive enzymes. (241) Types of phagocytes include neutrophils and macrophages

Asthma attack

Swelling and inflammation of airways - caused by the constriction of the small airways in the lung (bronchioles), making breathing difficult. (254).

Helper T cells

T cells that act as the immune system's commander (the main switch for the entire adaptive immune response); when macrophages properly alert helper T cells, they respond by calling out the body's specific defensive forces, and the immune response begins (246).

Secondary response

The adaptive immune response provoked by a subsequent exposure to an antigen. It differs from the primary response in that it starts sooner, is stronger, and occurs more quickly than the primary response. More lymphocytes respond to the antigen during subsequent exposures than during the first one (250).

Pathogens

The bacteria, viruses, protozoans, fungi, parasitic worms, and prions (infectious proteins) that cause disease. (239)

The Body's Defense System

The body generally defends you against anything that it does not recognize as being a part of you or belonging inside of you (239). Common targets: - pathogens - body cells that have turned cancerous

Cytotoxic T cells

The effector T cells responsible for the cell-mediated immune response that destroys antigen-bearing cells. Each cytotoxic T cell is programmed to recognize a particular antigen bound to MHC markers on the surface of a cellular pathogen, an infected or cancerous body cell, or on cells of a tissue or organ transplant.

First Line of Defense: Physical and Chemical Barriers

The skin and mucous membranes that form the first line of defense are physical barriers that help keep foreign substances from entering the body. They produce several protective chemicals. - physical barriers: unbroken skin helps shield the body from pathogens. A layer of dead cells, filled with keratin, forms the tough outer layer of the skin; it waterproofs the skin and makes it resistant to the disruptive toxins and enzymes of would-be invaders. - physical barriers: the mucous membranes, lining the digestive and respiratory passages, produce sticky mucus that traps many microbes and prevents them from fully entering the body. The contaminated mucous is moved by the beating of the cilia on the mucous membranes in our throat, and eliminated through coughing, sneezing, or swallowing. - physical barriers: saliva and tears contain an enzyme called lysozyme that kills some bacteria by disrupting their cell walls. - Chemical barriers: sweat and oil produced by glands in the skin wash away microbes. The acidity of the secretions slows bacterial growth, and the oils contain chemicals that kill some bacteria. - Chemical barriers: the lining of the stomach produces hydrochloric acid and protein-digesting enzymes that destroy many pathogens. - Chemical barriers: The acidity of urine slows bacterial growth (240).

Third Line of Defense: Adaptive Immune Response

This line of defense takes over when the body's first or second lines of defense fail to stop a pathogen, cancer cell, or foreign molecule from entering the body. It provides the specific responses and memory needed to target the invader. The immune system: recognizes and destroys specific pathogens or foreign molecules. Important characteristics of adaptive immune responses: (1) it is directed at a particular pathogen (ex: the measles). (2) it has a memory. (the immune system remembers a particular pathogen and, if the person is exposed to it again, attacks it quickly and viciously to prevent re-infection). (244-245)

Antibody-mediated immune response (specific defense)

This type of specific defense, defends primarily against antigens found traveling freely in intercellular and other body fluids - for example, toxins or extracellular pathogens such as bacteria or free viruses. - Effector B cells (aka plasma cells: the warriors of this branch) - Antibodies (the weapons of the warriors) (246).

Cell-mediated immune responses

This type of specific defense, protects against cellular pathogens or abnormal cells, including body cells that have become infected with viruses or other pathogens and cancer cells. The lymphocytes responsible for cell-mediate immune responses are a type of T cell called cytotoxic T-cell. Once activated cytotoxic T-cells quickly destroy the cellular pathogen, infected body cells, or cancerous cells by causing them to burst (246).

Treatment of Autoimmune disorders

Two-pronged: (1) any deficiencies caused by the disorder are corrected. (2) drugs are administered to depress the immune system (353).

inflammatory response

a reaction to tissue damage or injury; this response destroys invaders and helps repair and restore damaged tissue (242). There are four cardinal signs of inflammation, that occur at the site of a wound: (1) redness: the result of mast cells releasing histamine, in response to chemicals from damaged cells, causing blood cells to dilate (widen) in the damaged area and blood flow in the area to increase. (2) heat (warmth): the result of the increased blood flow elevating the temperature in the area of injury, to raise the metabolic rate of the body cells in the region and speed healing. (Heat also increases the activities of phagocytic cells and other defensive cells.) (3) swelling: histamine makes capillaries more permeable, or leakier, than usual. Fluid seeps into the tissues from the bloodstream, bringing with it many beneficial substances. (4) pain: caused by several factors. It usually prompts a person to protect the area to avoid additional injury. (243).

perforins

chemicals released by effector cytotoxic T cells, which cause holes to form in the target cell membrane. The holes are large enough to allow some of the cell's contest to leave the cell so that the cell disintegrates. The cytotoxic T cell then detaches from the target cell and seeks another cell having the same type of antigen.

Antihistamines

medicines that block the effects of histamines; they are most effective if taken before the allergic reaction begins (255). -Allergies tend to become less susceptible to antihistamines over time