Thursday, July 15, 1999

Structure and Function of the Human Body week 7

1. Compare and contrast non-specific and specific immunity. What is the difference between innate immunity, acquired immunity, active immunity, and passive immunity?

The immunity system works two ways. Non-specifically and specifically. The main difference between non-specific immunity and specific immunity have to do with the following: the response time, non-antigen specific vs. antigen specific and no memory vs. memory after exposure from the pathogen, foreign matter or abnormal cell.
In non-specific immunity (present at birth ) defense barriers are always present, capable of targeting non-specific antigens, has no immunological memory (immediate action only), and responds more immediate to invading organisms. In other words, the main function of non-specific immunity is preventing microbes from entering into the body by targeting antigens before hand or isolating them if microbes does enter the body, as in an inflammatory response (temporary repair, slows the spread of pathogen, and helps with tissue regeneration). An intact skin is the first line of defense for non-specific immunity. The skin prevents invasion of microbes. Other body defense surfaces includes mechanical and tactile protection the hair provides on the scalp and other parts of the body, sweat and sebaceous glands found in the epidermal (that flushes and washes away microbes and chemical agents), and epithelium lining in the digestive, respiratory, and urinary tract where acidity, enzymes, and mucus are secreted. Microbes are caught in the mucous found in the nose and respiratory. The stomach's acidity produces an environment that can hinder microbe growth or can destroy the microbe. Mucous in the urinary track attract microbes and flushes them out of the body. (pg 480)

Also included in non-specific immunity is phagocytes, the first line of cellular defense. There are two classes of phagocytes, microphages and macrophages. These 'Pac-Man' cells circulate in the blood system and enter the peripheral tissue, looking for microbes and pathogens to surround, and destroy. They are usually the first to encounter infection. (pg 479-480)

In the immunological surveillance, our body's immune system is surveying for abnormal cells to attack and destroy. This involves lymphocyte,NK (natural killer)cells. The NK cells pick up antigens on abnormal cells membranes. (pg 480)

The interferons are small proteins released by activated lymphocytes, macrophages, and tissue cells that have been exposed to a virus. In essence, cellular exposure with interferons produces anti-viral proteins; thereby, prevents viral replication inside the cell and slows the spread of the virus.

The complement system (complements antibodies' action) attacks and breaks down. Complement activation attracts phagocytes, stimulates phagocytosis, destroys plasma membranes (breaks down cellular walls), and stimulates inflammation. (pg 480-481)

In the inflammation process, mast cells play an important role. Mast cells are found in connective tissue and their main duty is to release chemicals that activates the body's defenses after an injury or infection. Once the mast cell is activated, blood flow increases, phagocytes are activated, capillary permeability increases the inflammation response, clotting reaction walls off region, regional temperature is increased, and specific defenses are activated. (pg 480)

In specific immunity, there is a lag time between exposure to the antigen and maximum response (antibodies). T-cells and B cells are naturally programmed in the bone marrow and thymus to attack only specific (nonself) antigens and not normal (self)body antigens found on normal cells. T-cells provide defense against abnormal cells and pathogens inside living cells (cell mediated immunity). B-cells provide defense against antigens and pathogens in body fluid (antibody-mediated immunity). Exposure to the pathogen or foreign cell results in immunological memory.

There are also two types of specific immunity, innate and acquired. Innate immunity is the genetically determined at birth and has no prior exposure to the antigen involved. The acquired immunity occurs when prior exposure and antibody production exist. Active and passive immunity are subdivision of acquired immunity. Active immunity is produced when specific antibodies develop in response to specific antigens. Active immunity can either occur through natural ( environmental) means or induced ( administration of antigens) means. Passive immunity is produced by transfer of antibodies from another person. Passive immunity can also occur through natural means such as in maternal breast milk or transferred of maternal antibodies across the placenta. (pg 482-483)

2. Explain the pathway of lymph once it enters into the lymphatic vessels to being “dumped” back into the blood stream. What materials or items could be found in the lymph? What happens to the lymph when it goes through the lymph node?

Unlike our circulatory system, where the blood stream is pumped by the heart, the lymphatic system is only a one way system that flows upward from the extremities (feet and hands), through the body towards the neck. This is accomplished through the normal movement of the respiratory and skeletal muscles and the overlapping arrangement of the endothelial cells found in the lymphatic vessels that promotes forward movement and prevents backflow. (pg 473)

Since the lymphatic vessels run parallel to the venous system, the start of the lymphatic system begins with the lymphatic capillaries which begins as a blind pockets in the peripheral tissue. These capillaries are lined with simple squamous epithelium and lack a basement membrane. This permits permeability of fluids, solids, and waste to flow into the lymphatic capillaries. (pg 473)

Lymphatic capillaries eventually flows into larger lymphatic vessels that eventually leads toward the trunk of the body. Like the venous system, valves are needed in the larger lymphatic vessels to prevent back flow due to the pressure in the vessel is low. The larger lymphatic vessels empty into two large lymphatic ducts, thoracic duct and right lymphatic duct. The thoracic duct collects lymph from the lower abdomen, pelvis, lower limbs and from the left half of the head, neck, and chest. It finally empties into the venous system near the junction between the left jugular vein and the left subclavian vein. The right lymphatic duct covers a smaller area. The right lymphatic duct collects lymph from the upper right quadrant of the body, the right arm, and the right side of the head and neck. It empties into the right subclavian vein (which is blood) that eventually goes into the right atrium of the heart back into the circulatory. I can imagine anything that leaks out from the tissue into the interstitial fluid leaks into the lymphatic capillaries; therefore, the thin epithelium found in the lymphatic capillaries permits water, protein molecules and other molecules, virus, bacteria, fungi and other pathogens are carried in the lymph. (pg 473)

When the lymph is processed through the lymph node, a filtration process is taking place removing waste products, some excess fluids, and purifying lymph fluid before it reaches the venous system. Afferent lymphatic vessels carry unfiltered lymph fluid through the nose. When the lymph flows through the sinuses of the lymph node, 99% of antigens are removed by macrophages (white blood cells). As the antigens are spotted and removed, this stimulates the T-cells and B-cells to activate which initiates the immune response. After the purification of the lymph fluid, the fluid is returned to the venous circulatory system through the efferent lymphatic vessels.

3. Compare and contrast T-lymphocytes and B-lymphocytes specific immunity mechanisms. In specific immunity, why does exposure (1st exposure compared to 2nd and subsequent exposures) matter?

Cells recognize antigens when those antigens are bound to membrane receptors of other cells. The structure of these antigen-binding membrane receptors is generally determine. Membrane receptors are called major histocompatibility complier (MHC) proteins. There are tow classes of MHC. Class I MHC protein are found in the plasma membrane of all nucleated cells. Class II MHC proteins are found in the membranes of lymphocytes of antigen – presenting cells (APC)
Class I MCH is MCH bend of display small peplicales molecules (chain of amino acid that are activated either by recognition such as in organ donation or by contact as in viral or bacterial which results in destruction of the abnormal cell. Class II MCH activate 7 cells to attack foreign cells, including bacteria and foreign proteins such as microglia in the CNS and macrophages in the liver (keep their cells) After the ACC breakdown the foreign antigens / pathogens – fragments of the foreign antigens are imprinted on their cell surfaces bound to class II MHC protein. T Cells that come in contract are APC membrane become activated initiating an immune response activating of T cell only occurs when MHC protein contains the specific antigen the T cell is program to detect T cells divide and differentiate into cells specific function in the immune response. These types are cytotoxic T cells, helper T cells, memory T cells and suppressor T Cells. (pg 486-488)

Cytotoxen T cells (killer t-cells) responsible for all medicated immunity they are activated by exposure to antigens bound to class I MHC proteins. They destroy their target by the following specific secretions: lymphotorein disrupt the cell metabolism, cytocrine tell the cell genes to die and perform which destructs the plasma membrane. T cells are activated by exposure to antigen bound to Class II MHC helper T Cells are activated by exposure to antigen bound to class II MHC proteins on antigen presenting cells through activation they divide to produce memory cells and more helper T cells. (pg 486-488)

Cytotoxin T cells and helper T cells developing into memory T cells these cell remain in reserve until the same antigen appears a second time around in which case they will become either cytotoxic T cells or helper T cells and enhance in speed and effectiveness of the immune response. Suppressor T cells have their major job which is to put the brakes on the response of other T cells and B cells by secreting cytolysis called suppression factors – suppression cells act after the initial immune system. (pg 486-488)

Initial response to antigen exposure is called primary response. Primary response takes approximately one-two weeks to develop peak antibody levels after exposure then recline. ICM modules are the first to appear in the blood stream followed by a slow rise in IGC. Secondly, in the primary response, antigens must activate specific B cells and B cells must then respond by differentiating into plasma cells. Memory B cells do not differentiate into plasma until cells are exposed to the same antigen a second time. After the 2nd exposure occurs, memory B cells respond quickly by dividing and differentiating into plasma cells that then secrete massive amount of antibodies. (pg 486-488)

During the second response, the body is ready with antibodies. The response is faster and stronger. The memory cells are already equipped to attack even with low levels of antigens. Immunization looks as a secondary response. because it stimulates the production of memory B cells under controlled condition. (pg 486-488)

B cells launch a chemical attack on antigens by going through a series of events that result in production of specific antibodies. Each B cells carries its own antibody molecule in its cell membrane. When a corresponding antigen appears in the interstitial luid gets well bound by B cells antibodies. The antigen enters the b cell by endocytosis and become displayed on class II MHC protein surface this is called sensitized activated help T cells encounting the antigen on the sensitizing B cell then release cytogens that trigger the activation of the B cell. The B cell then divides producing memory B cells and plasma cells that secrete antibodies.
Memory B cells like memory T cells remain on reserve to respond until second exposure of the same centigen at which time they respond by differenting into antibodies and secreting plasma cells. (pg 486-488)

Antigen antibody binding occurs between antigen binding sets on the antibody and antigenric determinant sites on the antigen. When an antibody molecule binds to its specific antigen an antigen antibody complex is formed. This is where they bind to certain positions of its exposed surface called antigenic determinate sites. (pg 486-488)

4. Immune responses are consistently occurring within our body and involve many complex steps. For the most part these mechanisms perform very well but there are 3 categories of complications and/or dysfunction that can occur within the immune system. List and describe each category and the cause of the dysfunction.

There are three classes of disorders that can result from a malfunctioning immune system. Autoimmune system is one class that targets normal (self) cells' antigens and tissues as foreign invaders. This causes the B-cells to produce specific antibodies to attack normal cells and tissues. These antibodies are called autoantibodies. Examples of autoimmune deficiency disorder is a situation that occurs in IDDM (insulin-dependent diabetes mellitus) where the auto-antibodies attack cells in the pancreatic islets. Another situation that can occur under autoimmune disorder is when antibodies start to associate normal protein amino acids sequencing with those of several viruses. Many viruses' proteins contain amino acids that closely resembles the amino acid sequence found in the nervous system protein. Complications caused by a viral infection or vaccination can result in a decease such as multiple sclerosis. Lastly, autoimmune disorder can be found in people who have an unusual genetic MHC (major histocompatibility complex) protein. People with this defect may sub-comb to such diseases as rheumatoid arthritis, grave's disease, psoriasis or pernicious anemia.

Immune deficiency disease is another class. In this case, there is an abnormal development of the immune system or the immune response is blocked. Children with SCIDC (severe combined immunodeficiency deceases) get to developed cell on immune response, total protected infected. Aids is another immunodeficiency decease caused by viral infection that targets helper T-cells which eventually causes an immune response to malfunctionencies.

Allergies is a third classes of the immune diffidences caused by antigens called allergens. In this case, the immune responds inappropriately excessively to the allergies. Immune hypersensitivity is a rapid form response to an antigen. The initial exposure does not trigger a response allergic reaction, but only lets the stage for a prone aggressive response second time around. The initial response only starts the process for IGE antibodies production and attach themselves to the cell membrane of the aphelia and mast cells. Later with the second exposure, these cells are activated and release histamine, heparin, several cytoganis, prostoglancilins, and other chemical into the surrounding tissues. The severity depends on the person's sensitively on areas envalve such as the body surface. - inflammation is restricted to that area, blood stream could be devastating in area prophylaxis is where the allergen affects the mast cells producing a severe reaction or even lethal reaction. The affects can produce cells-producing capillaries in the smooth muscle causing difficult breathing and of severe vasodilation causing circulatory collapse in the airway (Cana-phylactic shock)

5. Why can fevers be a good mechanism for the body? Why can they be a bad mechanism?
Fever is any temperature higher than 99°Fahrenheit. Fever is also your body's reaction to infection and illness. It helps the body to fight infections. Fever is only a symptom – along with other symptoms helps one determine your illness.
Fever as high as 103°for short time is helpful, because it helps the body fight infection by increasing the rate of metabolism, which enhances the phagocytosis, and increase enzymatic reaction. Fever occurs when the body's immune response is triggered by a protein called pyrogen (fever producing) . Pyrogens usually come from an outside source of the body and can stimulate production the inside of the body. Pyrogens causes the hypothalamus to increase the temperature set point (higher than 98.6° as an example). Examples of outside pyrogens are viruses, bacteria, fungi, and toxins.
High fevers over a long duration can cause problems for the body such as dehydration, and CNS problems which over the long run can be lethal to the body's homeostasis.

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