Immune System Flashcards
Name the two systems explored in this chapter.
The lymphatic system and the lymphoid organs and tissues.
What is the function of the lymphatic system?
To return fluids that have leaked from the vascular system back to the blood.
What are the three parts of the lymphatic system?
Lymphatic vessels, lymph nodes, and MALT (mucosa-associated lymphoid tissue).
What is the anatomical basis for the body’s defenses?
Lymphoid organs and tissues.
What are some examples of lymphoid organs and tissues?
Lymph nodes, spleen, thymus, and MALT.
What is the function of lymph nodes?
To filter lymph and remove foreign substances, such as bacteria and cancer cells.
What is the function of the spleen?
To filter blood and remove old or damaged red blood cells.
What is MALT?
Mucosa-associated lymphoid tissue, which protects mucous membranes from pathogens.
What is the relationship between the lymphatic system and the immune system?
The lymphatic system supports the immune system by returning leaked fluids and providing a site for immune cell activation and proliferation.
What is the purpose of exploring the developmental aspects of the lymphatic system and lymphoid organs and tissues?
To understand how these systems develop and mature over time, and how they may be affected by disease or injury.
List the functions of the lymphatic vessels.
The lymphatic vessels collect excess protein-containing interstitial fluid and return it to the bloodstream, and also transport lymph, a clear water fluid, which contains immune cells and waste products.
Describe the structure and distribution of lymphatic vessels.
Lymphatic vessels form a one-way system in which lymph flows only toward the heart. The transport of lymph begins in microscopic blind-ended lymphatic capillaries that weave between the tissue cells and blood capillaries in the loose connective tissues of the body. Lymphatic capillaries are widespread, but they are absent from bones (including bone marrow) and teeth.
Describe the source of lymph and mechanism(s) of lymph transport.
Lymph is formed from the excess interstitial fluid that is collected by the lymphatic capillaries. The lymphatic vessels have valves that prevent backflow of lymph, and they are also aided by the contraction of surrounding skeletal muscles and respiratory movements to propel lymph towards the heart.
What is the function of the minivalves in lymphatic capillaries?
To allow fluid to enter the lymphatic capillary when fluid pressure in the interstitial space is greater than the pressure in the lymphatic capillary.
What happens when the pressure is greater inside the lymphatic capillary?
The endothelial minivalve flaps shut, preventing lymph from leaking back out as the pressure moves it along the vessel.
What kind of particles can enter lymphatic capillaries easily?
Proteins in the interstitial space and larger particles such as cell debris, pathogens, and cancer cells when tissues become inflamed.
What happens to the particles that enter lymphatic capillaries?
They travel with the lymph to the lymph nodes, where they are removed by cells of the immune system.
Why is the process of pathogens meeting up with immune cells in lymph nodes critical?
Because it allows for the removal of disease-causing microorganisms such as bacteria and viruses.
Where are lymphatic capillaries present in the central nervous system?
They are present but restricted to limited locations in the meninges, where they help drain the extracellular fluids in the brain.
What are the two unique structural modifications that make lymphatic capillaries permeable?
Loosely overlapping edges of adjacent endothelial cells forming easily opened, flaplike minivalves and collagen filaments anchoring the endothelial cells to surrounding structures.
What is the function of the thoracic duct?
To drain lymph from the rest of the body and empty it into the blood at the junction of the left internal jugular and subclavian veins.
What is the function of the right lymphatic duct?
To drain lymph from the right upper limb and the right side of the head and thorax, and empty it into the blood at the junction of the right internal jugular and subclavian veins.
What are the mechanisms that promote lymph flow in the lymphatic vessels?
The milking action of active skeletal muscles, pressure changes in the thorax during breathing, and valves to prevent backflow.
What is the function of smooth muscle in the walls of lymphatic vessels?
To contract rhythmically and help pump lymph along.
What is the importance of movement of adjacent tissues in lymph transport?
It is extremely important in propelling lymph through the lymphatics.
What is the function of lacteals in the lymphatic system?
To transport absorbed fat from the small intestine to the bloodstream.
What is chyle?
Fatty lymph that drains from the fingerlike villi of the intestinal mucosa.
What are the three tunics of collecting lymphatic vessels?
They have the same three tunics as veins.
What is the anatomical distribution of lymphatic vessels?
It varies greatly between individuals, even more than it does for veins.
What are the major lymphatic trunks?
The paired lumbar, bronchomediastinal, subclavian, and jugular trunks, and the single intestinal trunk.
What are the two large ducts that lymph is eventually delivered to in the thoracic region?
The right lymphatic duct and the much larger thoracic duct.
What is lymphangitis?
A condition where the pathway of the associated superficial lymphatics becomes visible through the skin as red streaks that are tender to the touch due to severe inflammation of lymphatic vessels.
What can prevent the normal return of lymph to the blood?
Tumors blocking the lymphatics or surgical removal of lymph nodes.
Name three types of cells that play a crucial role in body protection and immune response.
Macrophages, dendritic cells, and reticular cells.
What is the function of lymphoid tissue in the immune system?
It houses lymphocytes and provides a site where they can be activated and proliferate, and it furnishes an ideal surveillance vantage point for lymphocytes and macrophages.
What is reticular connective tissue, and what is its function in lymphoid organs and tissues?
Reticular connective tissue is a type of loose connective tissue that dominates all the lymphoid organs except the thymus. It produces the reticular fiber stroma, which is the network that supports the other cell types in lymphoid organs and tissues.
What is the function of lymphatic vessels?
Lymphatic vessels return excess tissue fluid to the blood, return leaked proteins to the blood, carry pathogens to lymph nodes, and carry absorbed fat from the intestine to the blood through lacteals.
What are the two main varieties of lymphocytes, and how do they protect the body against antigens?
The two main varieties of lymphocytes are T cells and B cells. Activated T cells manage the immune response, and some of them directly attack and destroy infected cells. Activated B cells protect the body by producing plasma cells, daughter cells that secrete antibodies into the blood or other body fluids. Antibodies mark antigens for destruction.
Where is diffuse lymphoid tissue found in the body?
In virtually every body organ, with larger collections appearing in the lamina propria of mucous membranes such as those lining the digestive tract.
What are lymphoid follicles and where are they found?
Solid, spherical bodies consisting of tightly packed lymphoid cells and reticular fibers, often with lighter-staining germinal centers where proliferating B cells predominate. They form part of larger lymphoid organs such as lymph nodes, but isolated aggregations occur in the intestinal wall as Peyer’s patches and in the appendix.
What are the primary lymphoid organs and where do B and T cells mature?
The red bone marrow and the thymus. While both B and T cells originate in the red bone marrow, B cells mature in the red bone marrow and T cells mature in the thymus.
What are the secondary lymphoid organs and what is their function?
They include the lymph nodes, the spleen, and the collections of mucosa-associated lymphoid tissue (MALT) that form the tonsils, Peyer’s patches in the small intestine, and the appendix. They are where mature lymphocytes first encounter their antigens and are activated.
What are the two protective functions of lymph nodes?
Cleansing the lymph by removing and destroying microorganisms and other debris that enter the lymph, and immune system activation by strategically located sites where lymphocytes encounter antigens and are activated to mount an attack against them.
What is the structure of a lymph node and how does it support its defensive functions?
Most lymph nodes are bean-shaped and less than 2.5 cm in length, surrounded by a dense fibrous capsule from which connective tissue strands called trabeculae extend inward to divide the node into a cortex and medulla. The structure supports its defensive functions by acting as a lymph filter and strategically located sites where lymphocytes encounter antigens and are activated to mount an attack against them.
What is the function of lymph nodes in the immune system?
To filter lymph and activate lymphocytes to mount an immune attack against foreign agents.
How does lymph circulate through a lymph node?
Lymph enters through afferent lymphatic vessels, moves through the subcapsular sinus and smaller sinuses in the cortex and medulla, and exits through efferent lymphatic vessels at the hilum.
What is the structure of a lymph node?
A lymph node has a capsule, trabeculae, cortex, medulla, lymphoid follicles, germinal centers, subcapsular sinus, medullary cords, and medullary sinuses.
What is the function of the cortex in a lymph node?
The cortex contains densely packed follicles, many with germinal centers heavy with dividing B cells, and primarily houses T cells in transit.
What is the function of the medulla in a lymph node?
The medulla consists of medullary cords and sinuses, and both B and T lymphocytes are found here.
What is the role of macrophages in lymph nodes?
Macrophages reside on reticular fibers in lymph sinuses and phagocytize foreign matter in the lymph as it flows by.
What happens when lymph nodes are overwhelmed by foreign agents?
They become inflamed.
What is the consequence of lymph stagnation in a lymph node?
It allows time for lymphocytes and macrophages to carry out their protective functions.
What is the histological difference between the cortex and medulla in a lymph node?
The cortex contains densely packed follicles and primarily houses T cells in transit, while the medulla consists of medullary cords and sinuses and both B and T lymphocytes are found here.
Where is the spleen located in the body?
In the left side of the abdominal cavity just beneath the diaphragm.
What is the size of the spleen?
About the size of a fist.
What is the function of the spleen?
It provides a site for lymphocyte proliferation and immune surveillance and response. It also extracts aged and defective blood cells and platelets from the blood, removes debris and foreign matter, and performs blood-cleansing functions.
What are the blood vessels that serve the spleen?
The large splenic artery and vein.
What is lymphadenopathy?
A condition where lymph nodes become swollen, tender, and infected.
What are buboes?
Infected lymph nodes that are often pus-filled.
What happens when cancer cells enter lymphatic vessels and become trapped in lymph nodes?
Lymph nodes can become secondary cancer sites, particularly when metastasizing cancer cells enter lymphatic vessels and become trapped there.
What is the benefit of having fewer efferent than afferent lymphatics in lymph nodes?
Having fewer efferent than afferent lymphatics in lymph nodes slows down the flow of lymph, allowing more time for immune cells to carry out their functions.
What is a lymphoid follicle?
A lymphoid follicle is a spherical mass of lymphoid tissue that is not surrounded by a connective tissue capsule. B cells predominate in follicles, especially in their germinal centers.
Define Peyer’s patches.
Peyer’s patches are large clusters of lymphoid follicles located in the wall of the distal portion of the small intestine.
What is the function of Peyer’s patches?
To trap bacteria and particulate matter and generate many ‘memory’ lymphocytes for long-term immunity.
What is the appendix?
The appendix is a tubular offshoot of the first part of the large intestine that contains a high concentration of lymphoid follicles.
What is the function of the appendix?
To prevent bacteria from breaching the intestinal wall and generate many ‘memory’ lymphocytes for long-term immunity.
What are tonsils?
Tonsils are a ring of lymphoid tissue around the entrance to the pharynx that gather and remove many of the pathogens entering the pharynx in food or inhaled air.
What are the different types of tonsils?
The different types of tonsils are palatine tonsils, lingual tonsil, pharyngeal tonsil, and tubal tonsils.
What is the function of the tonsils?
To gather and remove many of the pathogens entering the pharynx in food or inhaled air.
What are the characteristics of the lymphoid tissue in the tonsils?
The lymphoid tissue of the tonsils contains follicles with obvious germinal centers surrounded by diffusely scattered lymphocytes. The tonsils are not fully encapsulated, and the epithelium overlying them invaginates deep into their interior, forming blind-ended tonsillar crypts.
What is the function of the thymus?
The thymus functions as a maturation site for T lymphocyte precursors.
What is the blood thymus barrier?
The blood thymus barrier keeps bloodborne antigens out of the thymus.
What is the stroma of the thymus made of?
The stroma of the thymus consists of epithelial cells.
Where is the thymus located?
The thymus is found in the inferior neck and extends into the superior thorax.
What happens in the thymus?
T lymphocyte precursors mature to become immunocompetent lymphocytes in the thymus.
What happens to the thymus as we age?
The thymus gradually atrophies and is replaced almost entirely by fibrous and fatty tissue.
What are thymic corpuscles?
Thymic corpuscles are bizarre structures consisting of concentric whorls of keratinized epithelial cells that are involved in the development of regulatory T cells.
How does the thymus differ from secondary lymphoid organs?
The thymus has no follicles because it lacks B cells and it is the only primary lymphoid organ.
Name the major functions of lymph nodes.
Cleanse lymph and serve as a site for lymphocyte activation and proliferation.
What is the function of the spleen?
Cleanses blood, removes aged or defective red blood cells, serves as a site for lymphocyte activation and proliferation, and stores platelets, monocytes, and iron.
What is the function of MALT?
Prevent pathogens from penetrating mucous membrane and serve as a site for lymphocyte activation and proliferation.
What is the function of the thymus?
Site of T cell maturation.
What is elephantiasis?
A tropical disease in which the lymphatics become clogged with parasitic roundworms, causing swelling in the lower limbs and scrotum.
What is Hodgkin’s lymphoma?
A malignancy of lymphoid tissue characterized by swollen, nonpainful lymph nodes, fatigue, and often intermittent fever and night sweats. It is treated with chemotherapy and radiation and has a high cure rate.
What is lymphadenopathy?
Any disease of the lymph nodes.
What is lymphangiography?
A diagnostic procedure in which the lymphatic vessels are injected with radiopaque dye and then visualized with X rays.
What is lymphoma?
Any neoplasm (tumor) of the lymphoid tissue, whether benign or malignant.
What is non-Hodgkin’s lymphoma?
Includes all cancers of lymphoid tissues except Hodgkin’s lymphoma. It involves uncontrolled multiplication and metastasis of undifferentiated lymphocytes, with swelling of the lymph nodes, spleen, and Peyer’s patches other organs may eventually become involved.
What is a sentinel node?
The first node that receives lymph drainage from a body area suspected of being cancerous. When examined for presence of cancer cells, this node gives the best indication of whether metastasis through the lymphatic vessels has occurred.
What is splenomegaly?
Enlargement of the spleen, typically caused by accumulation of infectious microorganisms and may be due to septicemia, mononucleosis, malaria, or leukemia.
What is tonsillitis?
Inflammation of the tonsils, typically due to bacterial infection. Tonsils become red, swollen, and sore.
Which body system helps protect nervous system structures from specific pathogens?
Immune system.
What is the role of lymphatic vessels in the endocrine system?
They pick up leaked fluids and proteins.
How do stress hormones affect immune activity in the endocrine system?
They depress immune activity.
What is the role of the spleen in the cardiovascular system?
It removes and destroys aged RBCs and debris, and stores iron, platelets, and monocytes.
What is the function of lymphoid follicles in the intestinal wall in the digestive system?
They prevent invasion of pathogens.
How does the urinary system maintain homeostatic balances of water, pH, and electrolytes in the blood for lymphoid/immune cell functioning?
By eliminating wastes.
What is the role of lymphocytes in the integumentary system?
They enhance the skin’s protective role by defending against specific pathogens via the immune response.
What is the function of hematopoietic tissue in the skeletal system?
It produces the lymphocytes (and macrophages) that populate lymphoid organs and provide immunity.
How does the skeletal muscle ‘pump’ aid the flow of lymph in the muscular system?
It aids the flow of lymph.
What is the role of shivering in the muscular system?
It produces heat at the beginning of a fever.
Define lymph nodes.
Lymph nodes are the principal lymphoid organs that are clustered along lymphatic vessels. They filter lymph and help activate the immune system.
What are the components of a lymph node?
Each lymph node has a fibrous capsule, a cortex, and a medulla. The cortex contains mostly lymphocytes, which act in immune responses the medulla contains macrophages, which engulf and destroy viruses, bacteria, and other foreign debris, as well as lymphocytes.
How does lymph flow through the lymph nodes?
Lymph enters the lymph nodes via afferent lymphatic vessels and exits via efferent vessels. There are fewer efferent vessels therefore, lymph flow stagnates within the lymph node, allowing time for its cleansing.
What is the function of the spleen?
The spleen removes bloodborne pathogens and aged red blood cells, provides a site for lymphocyte proliferation and immune function, recycles the breakdown products of hemoglobin, stores platelets and monocytes, and may be a hematopoietic site in the fetus.
What is MALT?
MALT (mucosa-associated lymphoid tissue) is a collection of lymphoid tissues that guard the body’s entryways against pathogens. It includes Peyer’s patches of the intestinal wall, lymphoid follicles of the appendix, tonsils of the pharynx and oral cavity, and follicles in the genitourinary and respiratory tract mucosae.
What is the function of the thymus?
The thymus provides the environment in which T lymphocytes mature and become immunocompetent. The thymus is most functional during youth.
What is the lymphatic system?
The lymphatic system includes lymphatic vessels, lymph, and lymph nodes. Lymphatic vessels return fluids that have leaked from the blood vascular system back to the blood. Lymphoid organs and tissues protect the body by removing foreign material from the lymph and bloodstream, and provide a site for immune surveillance.
What are the primary lymphoid organs?
The primary lymphoid organs are the red bone marrow and thymus, which are sites where lymphocytes develop and mature.
What are the secondary lymphoid organs?
The secondary lymphoid organs include lymph nodes, the spleen, and MALT. They are sites where lymphocytes encounter their antigens and are activated.
What is the function of lymphoid tissue?
Lymphoid tissue is an important element of the immune system. It houses macrophages and a continuously changing population of lymphocytes. It may be diffuse or packaged into dense follicles, which often display germinal centers (areas where B cells are proliferating).
What is the immune system?
The body’s defense against disease-causing organisms and cancerous cells.
What are surface barriers?
The skin and mucosae that provide the first line of defense against pathogens.
What are innate internal defenses?
Cells and chemicals that provide a rapid, non-specific response to pathogens.
What are lymphocytes and antigen-presenting cells?
Specialized cells that play a key role in the adaptive immune response.
What is the humoral immune response?
The production of antibodies by B cells to neutralize pathogens in the body.
What is the cellular immune response?
The activation of T cells to directly attack and destroy infected cells.
What happens when things go wrong with the immune system?
Autoimmune diseases, allergies, and immunodeficiency disorders can occur.
What are the developmental aspects of the immune system?
The immune system develops and matures throughout childhood and adolescence.
Where can you find a video about the chapter content being used in a healthcare setting?
Mastering A&P® > Study Area > Animations and Videos or use quick access URL https://bit.ly/3P8hiZa
What is the immune system?
A functional system consisting of a diverse array of molecules and immune cells that inhabit lymphoid tissues and circulate in body fluids.
What are the innate and adaptive defenses?
The innate and adaptive defenses are deeply intertwined. The innate responses are not as nonspecific as once thought and have specific pathways to target certain foreign substances. Proteins released during innate responses alert cells of the adaptive system to the presence of specific foreign molecules in the body.
What is the role of the immune system?
To protect the body from most infectious microorganisms, cancer cells, and transplanted organs and grafts, both directly by cell attack and indirectly by releasing mobilizing chemicals and protective antibody molecules.
What are surface barriers?
The skin and mucous membranes, along with the secretions these membranes produce, that act as the body’s first line of defense to keep invaders out of the body.
What is the innate defense system?
The innate defense system is the body’s first line of defense consisting of surface barriers and internal defenses such as antimicrobial proteins, phagocytes, and other cells to inhibit the invaders’ spread throughout the body.
What is the adaptive defense system?
The adaptive defense system functions like an elite fighting force equipped with high-tech weapons to attack identified foreign substances and takes considerably longer to mount than the innate defense response.
What is the hallmark of the second line of defense?
Inflammation.
What is the difference between humoral immunity and cellular immunity?
Humoral immunity primarily involves B lymphocytes, while cellular immunity involves T lymphocytes. Both are distinct but overlapping areas of adaptive immunity.
Name some innate internal defenses of the body.
Phagocytes, natural killer cells, antimicrobial proteins, and fever.
What is the inflammatory response and what are its components?
The inflammatory response is a protective response that enlists macrophages, mast cells, all types of white blood cells, and dozens of chemicals that kill pathogens and help repair tissue.
What are pattern recognition receptors and what is their role in immune responses?
Pattern recognition receptors are receptors that identify potentially harmful substances by recognizing molecules with specific shapes that are part of infectious organisms but not normal human cells. Toll-like receptors (TLRs) are a class of pattern recognition receptors that play a central role in triggering immune responses.
What are the body’s antimicrobial substances and what are their functions?
The body’s antimicrobial substances include acid, enzymes, mucin, defensins, and other chemicals. They function to inhibit bacterial growth, destroy bacteria, trap microorganisms, and control bacterial and fungal colonization in exposed areas.
What are the surface barriers of the body and how do they protect against pathogens?
The surface barriers of the body include intact skin epidermis, intact mucous membranes, nasal hairs, cilia, gastric juice, acid mantle of vagina, lacrimal secretion, saliva, and urine. They protect against pathogens by forming mechanical barriers, trapping microorganisms, inhibiting bacterial growth, and destroying pathogens.
What is the first line of defense against disease?
The surface membrane barriers are the first line of defense against disease.
What are TLRs and what is their function?
TLRs are pattern recognition receptors found on various cells, including macrophages and epithelial cells, that allow the cells to recognize invaders and initiate inflammation.
What are phagocytes and how do they work?
Phagocytes are cells that engulf and digest particulate matter, such as pathogens. Neutrophils and macrophages are types of phagocytes. They use receptors to bind to the particle and pull it inside, enclosed within a membrane-lined vesicle. The resulting phagosome then fuses with a lysosome to form a phagolysosome, which is then destroyed by lysosomal enzymes and other protein-digesting enzymes.
What is opsonization and how does it help phagocytosis?
Opsonization is the process of coating pathogens with opsonins, such as complement proteins or antibodies, which provide ‘handles’ to which phagocyte receptors can bind. This greatly accelerates phagocytosis of the pathogen.
What is the respiratory burst and how does it promote killing of pathogens?
The respiratory burst is a process in which neutrophils and macrophages release a deluge of highly destructive free radicals, oxidizing chemicals, and other substances that increase the phagolysosome’s pH and osmolarity. This activates other protein-digesting enzymes that digest the invader and promotes killing of pathogens.
What are defensins and how do they work?
Defensins are antimicrobial peptides that neutrophils use to pierce the pathogen’s membrane. They disrupt the membrane’s integrity and cause the pathogen to leak and die.
What are phagocytes and how do they kill their targets?
Phagocytes are defensive cells that ingest and destroy their targets. When they are unable to ingest their targets, they can release their toxic chemicals into the extracellular fluid. Neutrophils rapidly destroy themselves in the process, while macrophages are more robust and can survive to kill another day.
What are natural killer (NK) cells and how do they kill their targets?
Natural killer (NK) cells are a unique group of defensive cells that can kill cancer cells and virus-infected body cells before the adaptive immune system is activated. Unlike lymphocytes of the adaptive immune system, which only recognize and react against specific infected or tumor cells, NK cells are far less picky. They can eliminate a variety of infected or cancerous cells by detecting general abnormalities such as the lack of “self” cell-surface proteins called MHC. NK cells kill by directly contacting the target cell, inducing it to undergo apoptosis (programmed cell death).
What is inflammation and what are its beneficial effects?
Inflammation is a nonspecific response to any tissue injury caused by physical trauma, intense heat, irritating chemicals, or infection. Its beneficial effects include preventing the spread of damaging agents to nearby tissues, disposing of cell debris and pathogens, alerting the adaptive immune system, and setting the stage for repair.
What are the four cardinal signs of acute inflammation?
The four cardinal signs of acute inflammation are redness, heat, swelling, and pain. Impaired function may also be considered a fifth cardinal sign.
What are inflammatory chemicals and how do they contribute to the inflammatory process?
Inflammatory chemicals are released by injured or stressed tissue cells and immune cells. They can also be formed from chemicals circulating in the blood. Inflammatory chemicals dilate local arterioles, make local capillaries leakier, attract phagocytes to the injured area, and mobilize lymphocytes and other elements of adaptive immunity. They include histamine, kinins, prostaglandins, cytokines, and complement.
What is vasodilation and how does it contribute to inflammation?
Vasodilation of local arterioles causes local hyperemia, which brings more cells and chemicals of the immune system to the injured area. It accounts for the redness and heat of an inflamed region.
What is increased vascular permeability and how does it contribute to inflammation?
Inflammatory chemicals increase the permeability of local capillaries and venules, causing exudate to seep from the blood vessels into the surrounding tissue. Exudate contains clotting factors and antibodies and helps dispose of cell debris and pathogens. It also promotes the formation of edema, which contributes to the swelling of an inflamed region.
What are the four cardinal signs of acute inflammation?
Heat, redness, pain, and swelling.
What is the initial stimulus for acute inflammation?
Tissue injury.
What are the physiological responses to tissue injury?
Release of inflammatory chemicals, dilation of arterioles, increased capillary permeability, and local hyperemia.
What is leukocytosis?
Increased numbers of white blood cells in the bloodstream.
What is the purpose of leukocytes in acute inflammation?
To migrate to the injured area, cling to capillary walls, and pass through capillary walls to perform phagocytosis of pathogens and dead tissue cells.
What is the possible result of an abscess formed during acute inflammation?
It may need to be surgically drained before healing can occur.
What are granulomas?
Tumorlike growths that contain a central region of infected macrophages surrounded by uninfected macrophages and an outer fibrous capsule.
What is the potential danger of harboring pathogens walled off in granulomas?
If a person’s resistance to infection is ever compromised, the bacteria may be activated and break free, leading to clinical disease symptoms.
What are interferons and how do they protect against viruses?
Interferons are immune modulating proteins produced by body cells that block further protein synthesis and degrade viral RNA, thus interfering with viral replication. They diffuse to nearby cells and stimulate them to synthesize proteins that block viral replication. IFNs produced against a particular virus protect against other viruses too.
What are the different types of interferons and what are their physiological effects?
The different types of interferons are IFN alpha (α), beta (β), and gamma (γ). IFN alpha and beta have antiviral effects and activate NK cells. IFN gamma is secreted by lymphocytes and has widespread immune mobilizing effects, such as activating macrophages.
What is the complement system and how does it destroy foreign substances in the body?
The complement system is a group of at least 20 plasma proteins that normally circulate in the blood in an inactive state. Its activation unleashes inflammatory chemicals that amplify virtually all aspects of the inflammatory process. Activated complement also lyses and kills certain bacteria and other cell types. Complement activation by any of the three pathways involves a cascade in which proteins are activated in an orderly sequence, each step catalyzing the next. The three pathways converge at C3, which is split into C3a and C3b. Splitting C3 initiates a common terminal pathway that enhances inflammation, promotes phagocytosis, and can cause cell lysis.
What are the three pathways by which complement can be activated?
The three pathways by which complement can be activated are the classical pathway, the lectin pathway, and the alternative pathway.
What are antimicrobial proteins and how do they enhance our innate defenses?
Antimicrobial proteins are proteins that attack microorganisms directly or hinder their ability to reproduce. They enhance our innate defenses by providing a nonspecific defense mechanism that complements the effectiveness of both innate and adaptive defenses. The most important antimicrobial proteins are interferons and complement proteins.
What is fever and how does it benefit the body?
Fever is an abnormally high body temperature that is a systemic response to invading microorganisms. It benefits the body by causing the liver and spleen to sequester iron and zinc, which may make them less available to support bacterial growth. Additionally, fever increases the metabolic rate of tissue cells and may speed up repair processes.
What are pyrogens and how do they cause fever?
Pyrogens are chemicals released by leukocytes and macrophages when exposed to foreign substances in the body. They act on the body’s thermostat, raising the body’s temperature above normal.
What is cell lysis and how does it occur?
Cell lysis is the destruction of a cell’s membrane, which leads to the release of its contents. It occurs when C3b binds to the target cell’s surface and triggers the insertion of a group of complement proteins called MAC (membrane attack complex) into the cell’s membrane. MAC forms and stabilizes a hole in the membrane that allows a massive influx of water, lysing the target cell.
What is opsonization and how does it help phagocytes?
Opsonization is the process by which complement proteins, such as C3b, coat the surface of a microorganism, providing ‘handles’ that receptors on macrophages and neutrophils can adhere to. This allows them to engulf the particle more rapidly. An example of a molecule that acts as an opsonin is C3b.
Under what circumstances might NK cells kill our own cells?
NK cells might kill our own cells under circumstances where the cells are infected with a virus or have become cancerous, as these cells may display abnormal surface proteins that trigger the NK cells’ response.
What is humoral immunity?
Humoral immunity, also called antibody-mediated immunity, is provided by antibodies present in the body’s fluids (blood, lymph, etc.).
What is cellular immunity?
Cellular immunity, also called cell-mediated immunity, is when living cells (lymphocytes) provide protection against pathogens, cancer cells, and cells of foreign grafts.
What is the difference between humoral and cellular immunity?
Humoral immunity uses antibodies present in the body’s fluids, while cellular immunity uses living cells (lymphocytes) to provide protection.
What are the cardinal signs of inflammation?
The cardinal signs of inflammation are redness, heat, swelling, and pain.
What causes the cardinal signs of inflammation?
The cardinal signs of inflammation are caused by increased blood flow and permeability of blood vessels in the affected area.
What is the body’s third line of defense?
The adaptive immune system is the body’s third line of defense.
What is the major shortcoming of the adaptive immune system?
The major shortcoming of the adaptive immune system is that it must be primed by an initial exposure to a specific foreign substance (antigen) before it can protect the body against that substance.
What devastating diseases can result from the failure or disablement of the adaptive immune system?
Devastating diseases such as cancer and AIDS can result from the failure or disablement of the adaptive immune system.
What did experiments in the late 1800s reveal about specific immunity?
Experiments in the late 1800s revealed that animals surviving a serious bacterial infection have protective factors (the proteins we now call antibodies) in their blood that defend against future attacks by the same pathogen.
Define antigen.
Substances that can mobilize the adaptive defenses and are the ultimate targets of all adaptive immune responses.
What is the difference between complete antigens and haptens?
Complete antigens have immunogenicity and reactivity, while haptens have reactivity but not immunogenicity.
What are antigenic determinants?
Certain parts of an antigen that are immunogenic and antibodies or lymphocyte receptors bind to these antigenic determinants.
What are MHC proteins?
A group of glycoproteins that identify a cell as self and are strongly antigenic to other individuals.
What are the four key characteristics of the adaptive immune response?
It involves B and T lymphocytes, is specific, systemic, and has memory.
What is the difference between naturally occurring antigens and large simple molecules?
Naturally occurring antigens have a variety of antigenic determinants on their surfaces, while large simple molecules have little or no immunogenicity.
What are some examples of chemicals that act as haptens?
Certain drugs (particularly penicillin), poison ivy, animal dander, detergents, cosmetics, and a number of common household and industrial products.
Why are large proteins highly immunogenic and reactive?
They have hundreds of chemically different antigenic determinants on their surfaces.
What is the basis of transfusion reactions and graft rejection?
Self-antigens are strongly antigenic to other individuals.
What is the meaning of the term ‘antigen’?
A contraction of ‘antibody generating’ and refers to substances that can mobilize the adaptive defenses.
Define immunocompetence.
The ability of a lymphocyte to recognize and bind to a specific antigen.
What is self-tolerance?
The relative unresponsiveness of a lymphocyte to self-antigens to prevent attacking the body’s own cells.
What are primary lymphoid organs?
The lymphoid organs where lymphocytes mature, such as the thymus and red bone marrow.
What are secondary lymphoid organs?
All other lymphoid organs, such as lymph nodes and spleen, where immunocompetent B and T cells seed and encounter antigens.
What is the function of antigen-presenting cells (APCs)?
APCs play essential auxiliary roles in the adaptive immune response and are required for T cells to recognize their antigens.
What are the two distinct populations of lymphocytes involved in the adaptive immune response?
B lymphocytes (B cells) and T lymphocytes (T cells).
What is the difference between B cells and T cells?
B cells oversee humoral immunity and produce antibodies, while T cells constitute the cellular arm of adaptive immunity and do not produce antibodies.
What are the five general steps in the development, maturation, and activation of B and T cells?
Origin, maturation, immunocompetence, self-tolerance, and seeding secondary lymphoid organs and circulation.
What is clonal selection?
The process by which an antigen selects a particular immunocompetent lymphocyte for further development and activation.
What are homing signals (CAMs)?
Signals displayed on vascular endothelial cells that regulate lymphocyte movement into the tissues.
What determines which foreign substances our immune system can recognize and resist?
Our genes, not antigens we encounter.
What represents our genetically acquired knowledge of the microbes that are likely to be in our environment?
The immune cell receptors.
What determines which existing T or B cells will proliferate and mount the attack against an antigen?
The antigen itself.
What is a clone in the context of lymphocyte proliferation and differentiation?
An army of identical cells, all descended from the same ancestor cell.
What are effector cells in the context of lymphocyte proliferation and differentiation?
The cells that actually do the work of fighting infection.
What are memory cells in the context of lymphocyte proliferation and differentiation?
Cells that are able to respond quickly after any subsequent encounter with the same antigen.
Where do B cells mature?
In the bone marrow.
