Biol 242 chapter 22 Lymphatic system and Immunity

Define specificity and memory as properties of immunity.

(specifically adaptive immunity) specificity refers to the ability of the immune system to respond specifically to a pathogen, so the virus and bacteria will illicit different immune responses, different cells, different mediators will be produced as a result (T cells and B cells are capable of specificity) memory refers to the ability of your immune system to remember a pathogen so that when you see it again your immune response is much more immediate and you don't have to go through the process of educating your T cells or B cells with what that pathogen looks like because they already know because you have memory cells (memory B cells and memory T cells)

Differentiate MHC I and MHC II molecules. Identify where each is located

Infected body cells present endogenous (endogenous means inside the cell like a virus) antigens in association with MHC-I molecules APCs present exogenous (exogenous means that this a pathogen that is outside the cell like bacteria) antigens in association with MHC-II molecules

Briefly contrast the two general types of defenses in the body; innate and adaptive immunity.

Innate Immunity (Non-specific)Present at birth and includes defense mechanisms that provide general protection against invasion by a wide range of pathogens. Adaptive Immunity (Specific)Involves activation of specific lymphocytes that combat a particular pathogen or other foreign substance. The lymphatic system carries out immune functions of adaptive immunity (and some of innate immunity).

List and describe the general mechanisms of innate resistance including physical or external barriers, phagocytes, NK cells, interferons, the complement system, inflammation, and fever.

Innate immunity refers to a wide variety of body responses that serve to protect us against invasion of a wide variety of pathogens and their toxins interferons (communicating molecules) are cytokines that are involved in mediating immune responses, particularly viruses and are good at recruiting immune cells to kill the cells infected with that virus. Two lines of innate defense: 1. Skin and mucous membranes Mechanical Defenses: cilia, epiglottis, urine flow, vomiting, coughing, sneezing, tears, etc. Chemical Defenses: Sebum, lysozyme, gastric juices, etc. 2. Internal defenses: Immune cells fight back! Neutrophils, Macrophages (monocytes), Eosinophils, Basophils, Natural Killer (NK) Cells Antimicrobial proteins Phagocytes • Neutrophils, Macrophages Natural killer cells Inflammation Fever the complement system refers to a system of molecules that are involved in encapsulating an infected cell and recruiting immune cells to destroy that cell. inflammation and fever are the 2 typical responses of an innate immune response

Pyrexia

Is having a body temperature above the normal range

Differentiate "naïve" and "activated" immune cells. Identify locations where each lymphocyte gains immunocompetence.

Naïve means not immunocompetent Activated means it has become immunocompetent and it has seen a pathogen B cells- bone marrow T cells- thymus

Describe the steps involved in phagocytosis and give examples of important phagocytes in the body.

Phagocytes ingest and destroy the pathogen by a process called phagocytosis 1. Chemotaxis (the moving of the cell in a certain direction because of a chemical signal that is being produced) of phagocyte to microbe occurs. 2.Phagocyte adheres or attaches to microbe. 3. Pseudopods of the phagocyte engulf and internalize the microbe, forming a phagosome. 4. Lysosome fuses with the phagosome, forming phagolysosome. 5. Digestion of microbe occurs within phagolysosome. 6. Indegistible material is discharged. neutrophils, dendritic cells, macrophages, mast cells Phagocytes: digest unwanted cells and cell fragments (innate response)

Immunogenicity

Refers to the ability of a substance to provoke an immune response (ex: Antigen)

Describe inflammation and the difference between acute and chronic inflammation

Results from the body's attempt to address an invading pathogen, tissue death, or irritants. The goal of inflammation is to remove the cause of the damage, clear out dead cells, and help initiate tissue repair. Acute inflammation: The response to sudden body damage, such as cutting your finger. To heal the cut, your body sends inflammatory cells to the injury. These cells start the healing process. Chronic inflammation: Your body continues sending inflammatory cells even when there is no outside danger

sensitization and activation of B lymphocytes

Sensitization - the binding of antigens to the B cell membrane antibodies Activation - Helper T cells present same antigen to stimulate B cell Division - Stimulated B cells divide into many clones called plasma cells, which actively secrete antibodies Secretion - Each B cell secrete antibodies that will recognize only one antigenic determinant Differentiation - Active B cells also differentiate into Memory B Cells

activation of T lymphocytes

T cells are activated when they detect and bind to small fragments of antigens that are combined with to cell-surface glycoproteins called major histocompatibility complex (MHC) molecules >Lymphocytes respond to antigens bound to either class I or class II MHC proteins depending on the source of the MHC molecule and the antigen presenting cell >Class I MHC molecules are displayed on the surface of infected nucleated cells >Class II MHC molecules are displayed on the surface of phagocytes

Infection

The invasion of an organism's body tissue by disease-causing agents.

Briefly compare the primary and secondary immune responses.

This is basically your first exposure to a pathogen and your second exposure to a pathogen. secondary immune response is much faster and tends to be more robust, you get a stronger response

Describe the role of interleukins

a class of cytokines called IL-2, it is one of the ways T helper cells help to activate either cytotoxic T cells or B cells, this molecule helps activate these cells, it's a communication molecule

Describe the role of helper T cells CD4

activate other T cells and B cells >T Helper (TH) Cells: main role in immune response >Recognize antigen on the surface of antigen presenting cells >Secrete Interleukin II (T-cell growth factor), interferon and cytokines which stimulate lymphocyte activity >Production and activation of Cytotoxic T cells and more Helper T cells >Stimulate B cells to produce antibodies

Describe the mechanisms that antibodies use to render antigens harmless.

agglutination- enhances phagocytosis and reduces the number of infectious units to be dealt with opsonization- coating antigen with antibody enhances phagocytosis activation of complement- recruitment of complement proteins to the complement binding site of this antibody to help kill pathogens antibody-dependent cell-mediated cytotoxicity- antibodies attach to target cell cause destruction by non-specific immune system cells inflammation- attracts phagocytic and other defensive immune system cells (we either kill a pathogen by eating it with phagocytosis or poking it with holes until it lysis

Immunity

also called disease resistance.

Describe the structure of an antibody or immunoglobulin molecule, including light and heavy chains, antigen binding sites, complement binding sites, variable and constant segments and cell membrane binding sites.

antibodies are generally Y-shaped, the yellow and blue chains are called heavy chains, red chains are called light chains, antigen binding sites (variable region) are the V-shaped region of the Y, the stem region is the stem of the Y (referred to as the constant segment) also considered the cell membrane binding site because they are soluble (imbedded in the membrane) complement binding sites- only exist in soluble antibodies that are floating around and they are there to help recruit complement proteins that help kill that pathogen that once the antibody recognizes that pathogen

Describe the following; antigenic determinant sites (epitopes), MHC proteins, antibodies or immunoglobulins, complement cascade, and interferons.

antigenic determinant sites (epitopes)- portion of a foreign protein, or antigen, that is capable of stimulating an immune response. An epitope is the part of the antigen that binds to a specific antigen receptor on the surface of a B cell MHC proteins- Majorhistocompatibility Complex (MHC) Classes (I and II) antibodies or immunoglobulins- the soluble molecules that are produced by the humoral adaptive immunity system complement cascade- a way for proteins to opsonize a pathogen and recruit other cells to come kill a particular infected cell or pathogen, antibodies can initiate a complement cascade interferons (communicating molecules)- are cytokines that are involved in mediating immune responses, particularly viruses and are good at recruiting immune cells to kill the cells infected with that virus.

Define cytokine. Describe what the suffix "-itis" means.

any of a number of substances, such as interferon, interleukin, and growth factors, which are secreted by certain cells of the immune system and have an effect on other cells. (communicating cells) are small immunomodulating signaling molecules; the correct cytokine signaling is essential for inducing an appropriate immune response. -itis means swelling (inflammation)

Primary lymphatic organs

are organs where immune cells become immunocompetent which means capable of mounting an immune response. Primary lymphatic organs are: • Red bone marrow (B-Cells) • Thymus (T-Cells) *note: many immune cells progress from a "naïve" to an "activated" state upon encountering an antigen and this is a separate event from reaching immunocompetency.

Antigens

are typically proteins found on the pathogen surface that are unique to that pathogen which may be used by our immune system to elicit an immune response. Think of antigens as "pieces" of pathogens that can be recognized by our immune system and used to initiate an appropriate immune response.

Explain the concept of clonal selection and relate the importance of this process to effective immune responses.

clonal selection is all about specificity, it is quality control for specificity so when B cells are going through the process of making antibodies or when cytotoxic T cells are activated or when they are trying to become highly specific as well there is this process where your lymphatic tissues have these cells inside and they're going through this process of making a cells and testing its specificity and if this environment decides that its not specific enough it kinda modifies it clonal selection (making plasma cell) process is all about making a cell and testing how specific it is and if it isn't specific enough then I'm going to scrap it and try again, happens in germinal centers

MHC I respective functions in adaptive immunity in regard to antigen presentation.

exogenous antigen--> 1. digestion of antigen into peptide fragments 2. synthesis of MHC I molecule 3. antigen peptide fragments bind to MHC I molecules 4. packaging of MHC I molecules into a vesicle 5. vesicle undergoes exocytosis and antigen MHC I complexes are inserted into plasma membrane

Describe the role of memory T cells

function during a second exposure to antigen >Can survive a long time and give lifelong immunity from infection >Can stimulate memory B-cells to produce antibodies >Can trigger production of killer T cells

Describe the two types of adaptive immunity; humoral (antibody-mediated) cellular (cell-mediated) immunity.

humoral (antibody-mediated)- means that the focus is on producing antibodies that can target a pathogen, antibodies aren't cells they are immunoglobulins and they are specific to a pathogen, so in humoral we spend all of our time making antibodies that are specific to the pathogen it has just seen and then when we release those antibodies so they can go and find those pathogens the antibodies are used to target it and then recruit other cells to kill it. cellular (cell-mediated) immunity.- we train cells to go around and recognize those pathogens, so instead of having those soluble immunoglobulins we have whole cells that are going around with their T cell receptor looking for this particular pathogen and when they find the pathogen they do the same thing antibodies do, they bind to the cell that's infected or pathogen and they recruit other cells or other molecules to come and kill this cell. either way, they are both going to kill pathogens, it's just what tools we use to identify and kill the pathogen that's different between the two

Define hypersensitivity and immunodeficiency.

hypersensitivity is an allergic reaction immunodeficiency is a state in which the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. (HIV, chemotherapy, leukemia, etc)

Describe lymphocytes becoming immunocompetent, naïve lymphocytes, macrophages, and clones

immunocompetent cells are capable of mounting an immune response, sometimes they are called "mature" lymphocytes prior to achieving immunocompetency, they are considered naive, they haven't been educated yet. Once an immunocompetent cell encounters a pathogen and begins its role in initiating an immune response it is considered activated. B cells become immunocompetent in red bone marrow, while T cells become immunocompetent in the thymus (making these organs among the primary lymphatic organs) macrophages are antigen presenting cells (APC) Clones refer to the copies of mostly memory cells, they are exactly the same, and have been made in response to a specific pathogen, they just live in your body so when you see the pathogen again they become activated.

Secondary lymphatic organs and tissues include:

• Lymph nodes • Spleen • Lymphatic nodules • MALT (mucosa-associated lymphatic tissue)

Describe lymphatic vessel structure; describe the path and mechanisms of lymph formation and circulation.

just like veins only difference it it has a blunt end and they are one directional, the more pressure it accumulates the greater the pressure is exerted against the vessel wall, uses hydrostatic pressure to move, uses the same pumps the venous pumps use to travel through the body. lymphatic capillaries unite to form larger lymphatic vessels which resemble veins in structure but have thinner walls and more valves. lymphatic vessels in the subcutaneous tissue generally follow route of veins. lymphatic vessels of the viscera follow route of arteries. lymphatic vessels close at one end causing only a one way path for lymph to flow. Lymph return occurs very similarly to venous blood return in that it uses the same few mechanisms: 1. The Respiratory Pump 2. The Skeletal Muscle Pump 3. Smooth Muscle contraction when the vessel is distended. Lymphatic vessels begin as lymphatic capillaries, which are closed on one end. Lymphatic capillaries merge to form lymphatic vessels, which have thin walls and many valves (very similar to veins). Lymphatic capillaries drain interstitial fluid (much more permeable than blood capillaries). From the lymphatic vessels, lymph passes through lymph nodes and then into lymph trunks. -Lymph trunks include the lumbar, intestinal, bronchomediastinal, subclavian, and jugular trunks Lymph trunks then merge to form either the thoracic duct or the right lymphatic duct. -These ducts empty into the subclavian veins (just before the junction with the internal jugular veins)

Define lymph. List three main functions of the lymphatic system.

lymph is the fluid found within the lymphatic system, it is primarily derived from the interstitial fluid but these terms should not be used interchangeably drain interstitial fluid, transport dietary fats, carry out immune responses.

Describe the anatomy, location, and function of the following structures: lymph nodes, thymus, spleen, tonsils, and other MALT locations.

lymph nodes- encapsulated lymphatic nodule, it has an outer cortex, in the outer cortex there is germinal centers (where clonal selection happens), inner medulla, lymph nodes filter lymphs. thymus- located on top of the heart, it's encapsulated, a cortex, a medulla, pretty much just a bunch of T lymphocytes that are in the process of becoming immunocompetent spleen- found in the upper left quadrant of the abdomen, kinda lateral to the stomach, a little behind the stomach at the end of the pancreas, red pulp (involved with red blood cells), white pulp (involved with immune response), you can see the effects of a pathogen in the spleen because so much blood passes through it. tonsils- lymphatic nodules, pharyngeal tonsils, commonly known as adenoids, the palatine tonsils and the lingual tonsils, which are found at the base of the tongue MALT- mucosa-associated lymphatic tissue, best example we talked about is Peyer's patches, groupings of lymphoid follicles in the mucus membrane that lines your small intestine, but MALT can be found everywhere

Identify the components of the lymphatic system and briefly describe their functions. Briefly describe and/or recognize the lymphatic cells including NK cells, T lymphocytes, B lymphocytes, macrophages, and dendritic cells.

lymphatic nodules, lymph nodes, lymphatic capillaries, lymphatic vessels, lymphatic ducts, (major organs: lymph node, spleen, thymus, and bone marrow) NK cells- kills tumor cells and virus-infected cells. circulates in blood and migrates to tissue. B cells and T cells- The B cells produce antibodies that are used to attack invading bacteria, viruses, and toxins. The T cells destroy the body's own cells that have themselves been taken over by viruses or become cancerous. (they remember their responses) macrophages- living in tissues so they aren't in the blood, phagocytic cells that consume pathogen and cancer cells, stimulates response of other immune cells. dendritic cells- presents antigens on its surface, thereby triggering adaptive immunity. Present in epithelial tissue, including skin, lung tissue, and digestive tract, migrates to lymph nodes upon activation.

List places where naïve T lymphocytes hang out in the body.

naïve means they aren't immunocompetent, they are all the T lymphocytes that have left the bone marrow and are making their way to the thymus and are in the thymus, once they leave the thymus they are immunocompetent, that is why the thymus is were you find the most naïve T lymphocytes

List some factors that stimulate nociceptors during inflammation. Finally, explain why inflammation and fevers may be beneficial.

prostaglandins, bradykinins, substance P Like other forms of inflammation, a fever enhances the innate immune defenses by stimulating leukocytes to kill pathogens. The rise in body temperature also may inhibit the growth of many pathogens since human pathogens are mesophiles with optimum growth occurring around 35 °C (95 °F)

Describe the role of perforin

refers to a molecule that cytotoxic T cells use to poke holes in the plasma membrane of infected cells so the cell will burst

hapten

refers to a small molecule that can only elicit an immune response when bound to a larger "carrier" molecule.

Describe the role of B cells (plasma and memory)

>Plasma cells - B cells that are stimulated and begin actively secrete antibodies >Memory B cells provide secondary response (faster, more sensitive) turn into plasma cells and start making the antibody again

Describe the role of cytotoxic T cells CD8.

>Recognize and destroy host cells that are infected with viruses or bacteria, cancer cells, transplanted tissue (mediators) >Release protein called perforin which forms a pore in target cell, causing lysis of infected cells. >Produce cytokines, which promote phagocytosis and inflammation >Undergo apoptosis when stimulating antigen is gone.

Disease

A disorder of structure or function in an organism that produces specific signs or symptoms and is not a result of physical injury.

Describe the basic structure and cell composition of lymphatic tissue.

A lymph node is an organized collection of lymphoid tissue through which the lymph passes on its way to returning to the blood. Lymph nodes are located at intervals along the lymphatic system. Lymphoid tissue contains lymphocytes and other specialized cells and tissues that have immune system functions.

Define pathogen and recognize examples.

A pathogen is a bacterium, virus, or other microorganism that can cause disease. Examples: Influenza virus, HIV, Mycobacterium tuberculosis, Plasmodium falciparum, etc

List the four main signs of acute inflammation. Describe the events in acute inflammation, including vasodilation and increased blood vessel permeability, and the roles of mast cells, histamines, emigration, prostaglandins, neutrophils, macrophages, chemotaxis, opsonization, pyrogens, membrane attack complex, and pus.

Classic signs of acute inflammation are swelling, redness, pain, and heat. prostaglandins- a huge molecule responsible for vasodilation, causes pain, pyrogen histamines- are vasodilators (promote redness and heat) increased blood vessel permeability- vasoactive amines, bradykinin, leukotrienes, substance P, and more mast cells- generally are releasing the histamines, so when there are local mast cells in the area they are producing a lot of these molecules that are promoting inflammation, they are also phagocytes so they can help to clean up emigration- the process of a blood cell moving out of the bloodstream into interstitial fluid neutrophils- the biggest initiator of innate immune responses just because they exist in the largest amounts (there are more neutrophils than any other immune cell in your blood) they emigrate out of the bloodstream they get to the site of injury and they start phagocytosing debris and pathogens and if necessary they can present antigens to the adaptive immune response. Macrophages can do the same thing, there aren't as many macrophages as there are neutrophils pus- is an accumulation of neutrophils chemotaxis- refers to the process of a cell moving towards a chemical signal opsonization- (the process of coating a cell in these molecules and those molecules will subsequently recruit more molecules to come to kill that cell) is the process of coating an infected cell or pathogen in proteins that are either complement proteins or an antibody. It's basically a coating of a pathogen in a molecule that is going to be responsible for destroying that cell or pathogen. pyrogen- are substances that induce fever, they basically cause the hypothalamus to reset its thermostat the membrane attack complex- is the end result of the complement cascade, another way to kill cells.

MHC II respective functions in adaptive immunity in regard to antigen presentation.

Exogenous antigen--> 1. phagocytosis or endocytosis of antigen 2. digestion of antigen into peptide fragments 3. synthesis of MHC II molecules 4. packaging of of MHC II molecule into a vesicle 5. vesicles containing antigen peptide fragments and MHC II molecules fuse 6. antigen peptide fragments bind to MHC II molecule 7. vesicle undergoes exocytosis and antigen MHC II complexes are inserted into plasma membrane

antigen-presenting cells (APCs)

those cells capable of "seeing" an antigen in the body, processing it, and "presenting" it to another immune cell. The three major antigen-presenting cells, called professional APCs, in the body are B Lymphocytes, macrophages, and dendritic cells although other cells can present antigens, but do it much, much less frequently. These cells can "present" an antigen to T-helper cells who are unable to "see" antigens, but have some of the most important roles in eliciting an immune response.

Antigen recognition

For an immune response to occur, B cells and T cells must recognize that a foreign antigen is present (antigen recognition). • B cells can recognize and bind to antigens in lymph, interstitial fluid, or blood plasma • T cells only recognize fragments of antigenic proteins that are processed and presented in a certain way, they cannot directly recognize a pathogen. the cell recognizes that a different cell is displaying an antigen