Chapter 7: The Lymphatic and Immune System PDF

December 2, 2024 Chapter 7: The Lymphatic and Immune System Lymphatic system- consists of lymphatic vessels and lymphatic organs. Provides homeostatic functions for our bodies. Part of the immune system. Homeostasis functions: - Lymphatic capillaries absorb excess inter...

December 2, 2024 Chapter 7: The Lymphatic and Immune System Lymphatic system- consists of lymphatic vessels and lymphatic organs. Provides homeostatic functions for our bodies. Part of the immune system. Homeostasis functions: - Lymphatic capillaries absorb excess interstitial fluid - Lymphatic capillaries absorb fats from the digestive tract and transport them to the bloodstream - Lymphoid organs help defends the body against disease Lymphatic vessels- form a one-way system of vessels that move fluid from tissues to the cardiovascular system Interstitial fluid- the primary component of lymph; mostly water, but also contains solutes (nutrients, electrolytes, and oxygen) derived from blood plasma. Additionally, interstitial fluid contains cellular products (hormones, enzymes, and cellular waste). Lymphatic organs- divided into primary and secondary lymphatic organs. Primary lymphatic organs are the red bone marrow and the thymus. Secondary lymphatic organs are the lymph nodes and the spleen. Primary lymphatic organs: Red bone marrow- produces all types of blood cells Children have red bone marrow in most bones Adults have red bone marrow in: the sternum, vertebrae, ribs, pelvic girdle, humerus, femur Red bone marrow produces red blood cells and five types of white blood cells: Neutrophils, eosinophils, basophils, lymphocytes, monocytes Lymphocytes- divided into B cells and T cells B cells ( B lymphocytes) mature in the bone marrow. Any B cell that reacts to body cells is destroyed in the bone marrow and does not enter circulation to prevent autoimmune disorders. T cells ( T lymphocytes) mature in the thymus Thymus- soft-bodied and bilobed organ located in the cavity between the trachea and the sternum which decreases in size as children grow into adulthood Thymus functions: - Produce hormones (like thymosin- aids in the maturation of T lymphocytes) - Maturation site of T lymphocytes- only ~5% of these cells ever leave the thymus To leave the thymus, T cells have to demonstrate that they can attack a pathogen and that they will not attack body cells Without mature T cells, the body cannot adequately respond to specific infections Secondary lymphatic organs: Spleen- filters blood; largest lymphatic organ, located in the upper left part of the abdominal cavity Within the spleen, macrophages engulf pathogens and debris Lymph nodes- occur along lymphatic vessels; each of their multiple compartments are filled with lymph, and lymphocytes and macrophages (which attack pathogens and cancer cells) Immunity- the capability of killing or removing foreign substances, pathogens, and cancer cells - Innate (non-specific) immunity - Adaptive immunity Innate (non-specific) immunity - Physical and chemical barriers - skin- prevents the entry of microbes - mucous membranes- trap invading pathogens - perspiration, saliva, and tears- contain lysozyme (antibacterial enzymes) - acidic pH- stomach and vagina - microbiome- beneficial bacteria in our system Inflammatory response- employs neutrophils and macrophages to surround and kill invading pathogens - Symptoms of IR: redness, heat, swelling, pain Histamine- a chemical mediator released by damaged tissue cells and mast cells which cause the capillaries to dilate and become more permeable Excess fluid from leaky capillaries cause swelling (which presses on nerves) and pain These conditions summon white blood cells to the region Neutrophils are the first WBCs to arrive, and they phagocytize (eat) debris, dead cells, and bacteria If neutrophils are overwhelmed, they release cytokines Cytokines- proteins that attract more WBCs including monocytes Monocytes are longer-lived cells that become macrophages Macrophages are more powerful phagocytes than neutrophils Complement system- composed by a number of blood plasma proteins that increase the immune response of one or more specific immune responses Complement proteins can: - Trigger mast cells to release histamine - Attract phagocytes to a specific location - Bind directly to bacteria can cause them to burst Interferons- proteins produced by virus-infected cells that cause uninfected cells to prepare for viral infection by producing substances that interfere with viral replication Antigen- a large protein structure that the immune system recognizes as a foreign body Fragments of: - Bacteria - Viruses - Molds - Parasitic worms Adaptive defenses primarily depend on B and T cells (B and T lymphocytes) - Each lymphocyte has a single kind of receptor to combine with a specific antigen (like a lock and key) Adaptive immunity pathways - Cell-mediated immunity - Antibody-mediated (humoral) immunity Cell-mediated immunity- T cells target and destroy any cells that present a specific antigen - Helper T cells may come into contact with an antigen and release cytokines to call cytotoxic T cells to the area - Cytotoxic T cells either phagocytize or trigger apoptosis in infected cells Slide 47 December 5, 2024 Adaptive Immunity Pathways - Cell mediated immunity - Antibody-mediated (humoral) immunity Antibody-mediated (humoral) immunity - An antigen binds with a B cell’s receptor - The B cell then undergoes rapid clonal expansion, creating B memory cells, and plasma cells - The plasma cells created secrete antibodies for the original antigen - Only the B cells that have receptors that fit the antigen undergo clonal expansion - Most cloned B cells become plasma cells, which circulate in the blood and lymph and constantly excrete antibodies keyed to the original antigen - A minority of the cloned B cells become B memory cells, which have a long life and have the same receptors - Once the infection has passed, any remaining plasma cells undergo apoptosis (programmed cell death) Antibody structure - Y- shaped with two antigen binding sites Antibody function - Many antibodies will bind with the antigens, covering the offending molecule so that it can't bind - Antibodies then call for other white blood cells Antibody classes: IgG IgM IgA IgD IgE IgG: - Main antibody type in circulation - Crosses the placenta from mother to fetus - Binds to pathogens - Activates compliments - Enhances phagocytosis by WBCs IgM: - Found in circulation - Largest antibody - First antibody formed by newborns - First antibody formed in any new infection - Activates compliment and clump cells IgA: - Main antibody in saliva and breast milk - Prevents pathogens from attaching to epithelial cells in the digestive and respiratory tracts IgD: - Antibody found on the surface of immature B cells - Signifies readiness of B cells IgE: - Antibody found as antigen receptors on mast cells - Responsible for immediate allergic response and protection against certain parasitic worms Cytotoxic T cells- specialized T lymphocytes with storage vacuoles that contain perforins and storage vacuoles that contain granzymes (an enzyme that causes apoptosis) Helper T cells- specialized T lymphocytes that regulate immunity by secreting cytokines - B lymphocytes cannot be activated without T cell help - HIV (which causes AIDS) attacks T cells, which leaves patients vulnerable to opportunistic infections, which may eventually cause death Memory T cells- remain within the body and can jump-start an immune response to an antigen previously present in the body Active immunity- occurs when an individual produces antibodies against an antigen Passive immunity- occurs when an individual is given prepared antibodies via an injection Active immunity - Develops naturally after a person is infected with a pathogen - Can be artificially developed by expose to the antigen Immunization- Vaccine- Active immunity- vaccines - Vaccines have traditionally been composed of either the pathogen itself or their products that have been treated to no longer be virulent (able to cause disease) - Today we can use genetic engineering to make bacteria mass produce a protein from the pathogen to make a vaccine (Hep B and Malaria) - Initially, vaccines typically illicit an immune response that peaks around 14 days after injection - A second dose of vaccine (booster) will typically illicit a much faster and higher concentration of antibodies, because memory B and T lymphocytes are already present Passive immunity- occurs when an individual is given prepared antibodies via an injection (or via other means) Because the infected individual’s body (plasma cells) is not responsible for making the antibodies, the immunity is temporary Passive immunity is commonly achieved in infants from IgG antibodies that have crossed the placenta from their mother Within a few months, these antibodies will disappear, and the infant will be susceptible to infection even though passive immunity does not last, it is sometimes used to prevent illness in a patient who has unexpectedly been exposed to an infectious disease This can be done by injecting the patient with gamma globulin of serum that contains antibodies (sometimes taken from individuals who have recovered from the disease) Acquired immunodeficiency syndrome (AIDS)- inability of the acquired immune system to respond to opportunistic pathogens because of a low helper T cell count; caused by HIV Human immunodeficiency virus (HIV)- virus that infects and destroys T helper cells and macrophages; causes AIDS if untreated Opportunistic infection- an infection that can only occur because the patient’s immune system is compromised Allergies- a hypersensitivity to a substance, like pollen, food, animal hair, or mold that would ordinarily do no harm to the body Allergen- an antigen that elicits an allergic response Immediate allergic response- response within seconds to be exposed to an allergen; caused by IgE antibodies attached to receptors on mast cells and basophils Anaphylactic shock- an immediate allergic response that occurs when an antigen enters the bloodstream; characterized by a life-threatening sudden drop in blood pressure due to the increased permeability of capillaries in response to a flood of histamine. Often treated with epinephrine. Delayed allergic response- immune response initiated by T cells at the site where an allergen contacts the body - Used to test for tuberculosis (TB): when the antigen is injected under the skin, the site will become red and hardened if the patient has previously been exposed to TB - Contact dermatitis occurs at the point where skin is exposed to the antigen; common examples include poison ivy, jewelry, cosmetics, latex, ect. Other immune system disorders Organ rejection - Many human organs could easily be transplanted between patients if not for the immune system recognizing the new tissue as “not self” (MHC antigens) - Immunosuppressive drugs can be administered to prevent the production of certain T cell cytokines Severe combined immunodeficiency disease (SCID) - Characterized by both the antibody and cell-mediated immune responses being either inadequate or lacking - Has been successfully treated with bone marrow transplant and/or gene therapy Autoimmune disease - Occurs when cytotoxic T cells or antibodies attack the body’s own tissues - Exact cause is unknown, but it appears to have both genetic and environmental components - Women more likely to develop autoimmune disorders than men Autoimmune disease- the hygiene hypothesis - Living in anthropogenic (human-made) environments limits our contact with a variety of pathogenic worms and bacteria - Our immune systems may require irregular contact with these pathogens to maintain an understanding of what is “self” and “not self” - Modern pollutants and antibiotics may also be contributing to the confusion of our immune systems Autoimmune diseases that follow infections - Rheumatic fever- antibodies introduced into throat to fight the streptococcal infection also react with the heart muscle - Causes an inflammatory response in the heart that damages the heart muscle and valves Rheumatoid arthritis- causes chronically inflamed joints - Antibodies, compliments, neutrophils, activated T cells, and macrophages all attack the cartilage of the joints Systemic lupus erythematosus (SLE)- various symptoms including facial rash, fever, and joint pain - Patients produce high levels of anti-DNA antibodies, which interferes with tissues throughout the body - Damage to central nervous system, heart, and kidneys can be fatal Myasthenia gravis- antibodies attach to muscle cells - Causes muscle weakness and eventual death from respiratory failure