Ch. 22 - Immune System and the Body's Defense

Upon secondary exposure to an antigen determinant, helper T-lymphocytes _________

release cytokine interleukin-2.

Typically, a lymphocytes will encounter its first exposure to a foreign antigen in the ___________

secondary lymphatic structures.

When interferon from one cell attaches to a second cell _______

the recipient cell makes enzymes that degrade viral RNA and DNA.

Describe immunologic memory, and explain how it occurs

Ability of the immune system to quickly + specifically recognize an antigen that the body has previously encountered Initiate a corresponding immune response

Explain immunogenicity, and list attributes that affect it

Ability of an antigen to cause an immune response Attributes: - Degree of foreignness - Size - Complexity - Quantity of antigen Increase in one or more of these increases the antigen's ability to elicit an immune response

List the risks of a high fever

(>100 degrees F) Potentially dangerous because of the changes in metabolic pathways + denaturation of body proteins Seizures may occur at sustained temp >102 F Irreversible brain damage can occur temp >106 F Death is likely when body temp reaches 109 F

List the cardinal signs of inflammation, and why each occurs

(Major representative characteristics) Redness - increased blood flow Heat - increased blood flow + increased metabolic activity within area Swelling - increase in fluid loss from capillaries into interstitial space Pain - stimulation of pain receptors fro compression due to accumulation of IF + chemical irritation Loss of function - (may occur in more severe cases due to pain and swelling)

Describe the cells that function as part of the nonspecific internal defenses in providing innate immunity

1) Activities of various types of cells 2) Chemicals such as interferon + complement 3) Physiologic process that include the inflammatory response + development of a fever

Types of leukocytes of the immune system

1) Three types of granulocytes - neutrophils, eosinophils, basophils 2) Monocytes that become macrophages or dendritic cells when they exit the blood vessels + take up residence in blood tissue 3) Three types of lymphocytes - T-lymphocytes (T-cells), B-lymphocytes (B-cells), and NK (natural killer) cells

Define a fever and describe how it occurs

Abnormal elevation of body temperature (pyrexia) of at least 1 degree C from typically accepted core body temp of 37 degrees C (98.6 F) Results from release of pyrogens that are released from infectious agents or immune cells in trauma, infection, drug reactions, and brain tumor

Explain the effector response of helper T-lymphocytes

Activate cytotoxic T-lymphocytes through release of cytokines Formation + activity of cells of innate immune system, including macrophages and NK cells

Describe how both active and passive immunity can be acquired naturally and artificially

Active immunity - Naturally - individual is directly exposed to antigen of infectious agent - Artificially - exposure occurs through vaccine Passive immunity - Naturally - transfer of antibodies from mother to fetus across placenta (IgG) or to the baby in mother's breast milk (IgA, IgM, IgG) - Artificially - serum contains antibodies against a specific antigen

Define active immunity and passive immunity

Active immunity - results from direct encounter with a pathogen or foreign substance that results in production of memory cells - Can be obtained either naturally or artificially Passive immunity - obtained from another individual or an animal - Can be obtained naturally or artificially

Fungi

Composed of eukaryotic cells - Have a cell wall external to plasma membrane Includes mold, yeast, multicellular fungi - Produce spores Proteolytic enzymes released induce inflammation that causes redness + swelling of infected area In health individuals, disease usually limited to skin, scalp, nails

Select all that are true regarding memory: Antigen challenge is required for generation of memory cells. Upon first exposure, symptoms of sickness may develop. Upon second exposure, the antigen is often destroyed before symptoms may develop. Memory B-lymphocytes and T-lymphocytes are responsible for immunologic memory.

All are true

List the functions of the antigen-binding site and Fc region or antibodies, and briefly describe how each occurs

Antigens are effective against antigens through use of: 1) antigen-binding region within variable region (two arms of Y-shaped antibody) 2) Fc constant region (stem of Y-shaped antibody)

Describe antigen-presenting cells, and list cells that serve this function

Any immune cell that functions specifically to communicate the presence of an antigen to both helper T-lymphocytes and cytotoxic T-lymphocytes Cells that serve this function: - Dendritic cells - Macrophages - B-lymphocytes

Five major classes of infectious agents

Bacteria Viruses Fungi Protozoans Multicellular parasites

Proinflammatory Chemical-Secreting Cells

Basophils + Mast cells - Serve as chemotaxic chemicals (molecules that attract immune cells as part of inflammatory response) - Release granules during inflammatory response (histamine, heparin, eicosanoids)

Margination

CAMs on leukocytes adhere to CAMs on endothelial cells of capillaries "Cellular Velcro"

Explain the general functions of interferons

Category of cytokines Process of how IFNs serve as a nonspecific defense mechanism against spread of any viral infection: 1) Body cell is first infected with a virus 2) In response, the virus-infected cell releases both IFN-α and IFN-β 3a) IFN-α and IFN-β bind to receptors of neighboring body cells. This triggers these cells to synthesize enzymes that both destroy viral RNA or DNA and inhibit synthesis of viral proteins. These cells are protected from becoming infected with the virus. 3b) IFN-α and IFN-β also stimulate NK cells to destroy the virus-infected cells by apoptosis 4) Nk cells release IFN-γ to stimulate macrophages to aid in destroying there virus-infected cells through phagocytosis

Diapedesis

Cells exit the blood by "squeezing out" between vessel wall cells, usually in post capillary venues, and then migrate to site of infection

Define antibody titer

Circulating blood concentration of antibody against a specific antigen Can be a measure of immune response

Which of the following is not an antigen-presenting cell? Macrophages B-lymphocytes Cytotoxic T-lymphocytes Dendritic cells

Cytotoxic T-lymphocytes

Define antigen presentation

Display of antigen on a cell's plasma membrane surge Necessary process performed by other cells so that T-lymphocytes can recognize an antigen - All nucleated cells of the body - Antigen-presenting cell (APC)

Define the complement system, and describe how it is activated

Diverse array of proteins (min. 30) produced by our liver + released into blood Identified with letter "C" followed by a number Very abundant Make up approximately 10% of blood serum proteins Activation of complement occurs following entry of a pathogen into body - Classical pathway: compliment protein binds to an antibody that has previously attached to a foreign substance - Alternative pathway: surface polysaccharides of certain bacterial + fungal cell walls bind directly with complement protein

Formation and "docking" of MHC Class I Molecules in Nucleated Cells

Endogenous pathway in a healthy cell

A patient has a parasitic infection. Upon examination of a blood dslmplr under the microscope, an abundance of granulocytes are present. These are likely _________.

Eosinophils

Skin

Epidermis + Dermis - Stratified squamous epithelium forms epidermis - Areolar and dense irregular connective tissue forms dermis - Provide physical, chemical, biological barrier for a body surface Normal flora - Commensal microflora, including nonpathogenic bacteria - Help prevent growth of pathogenic microbes Exfoliation - Sloughing off of epidermal cells - Removes potential pathogens from skin surface Hyaluronic acid - Mucopolysaccharide with a gel-like consistency that is located in areolar tissue of dermis - Slow migration of microbes that have penetrated the epidermis Sebaceous (oil) gland secretions - Sebum that contain lactate + fatty acids - Creates a low pH (3-5) that interferes with growth of microbes Sweat gland secretions - Contain lysosome, defensins, dermicidin - Help wash away microbes; contain antibacterial + anti fungal substances

Mucous Membranes

Epithelial and connective tissue - Lining if respiratory, gastrointestinal, urinary, reproductive tracts; contain hyaluronic acid - Provide physical, chemical, biological barrier of body structures exposed to external environment Normal flora - Commensal microflora, including nonpathogenic bacteria - Help prevent growth of pathogenic microbes Mucus - Formed from hydrated mucin; contains lysozome, defensins, and IgA - Thick secretions that helps trap microbes; contains antimicrobial substances

Formation and "docking" of MHC Class II Molecules in Antigen-Presenting Cells

Exogenous pathway

T or F: A hapten is an antigen capable of stimulating antibody production.

False

Activation of Helper T-lymphocytes

First signal - direct physical contact between MHC class II molecule of APC + TCR of helper T-lymphocyte - APC housed in secondary lymphatic structure or migrates there from skin - Helper T-lymphocyte binds to APC to inspect antigen Second signal - takes place when other receptors of APC interact with receptors of helper T-lymphocytes - Helper T-lymphocytes induced to synthesize + release cytokine interleukin 2 - T-lymphocytes activated and proliferate to form clones of helper T-lymphocytes (activated helper T-lymphocytes + memory helper T-lymphocytes)

Activation of cytotoxic T-lymphocytes

First signal - similar to naive helper T-lymphocyte; direct physical contact is made between TCR and peptide - Interaction stabilized by CD8 of cytotoxic T-lymphocyte binding to other regions of MHC class I molecule Second signal - binding of IL-2 released from helper T-lymphocytes - IL-2 acts a paracrine hormone to stimulate cytotoxic T-lymphocyte - IL-2 required for cytotoxic T-lymphocytes to become fully activated - Cytotoxic T-lymphocytes proliferate + differentiate into clones becoming activated cytotoxic T-lymphocytes + others developing into memory cytotoxic T-lymphocytes

Match the antigen type with its description and example: Foreign antigen description Foreign antigen example Self-antigen description - Introduced from outside the body Molecules produced by the body Pollen

Foreign antigen description - Introduced from outside the body Foreign antigen example - Pollen Self-antigen description - Molecules produced by the body

Identify the three significant events that occur in the lifetime of a lymphocyte

Formation of lymphocytes - Occurs within primary lymphatic structures (red bone marrow + thymus) - T-lymphocytes and B-lymphocytes become able to recognize only one specific foreign antigen Activation of lymphocytes - Migrate to secondary lymphatic structures where they are housed - Lymphocytes have first exposure to antigen that they bind Effector response - Specific action of T-lymphocytes and B-lymphocytes to help eliminate antigen at the site of infection - Antibodies enter blood + lymph and are transported to site of infection

Interleukin (IL)

Function - Regulates immune cells Source - T-lymphocytes - Macrophages - Endothelial cells - Other various cells Designation - IL followed by number

Tumor necrosis factor (TNF)

Function - destroys tumor cells Source - T-lymphocytes - Macrophages - Mast cells - Dendritic cells Designation - TNF followed by Greek letter

Colony-stimulating factor (CSF)

Function - stimulates leukopoiesis in bone marrow to increase synthesis of a specific type of leukocytes Source - T-lymphocytes - Monocytes Designation - First letter of cell(s) it is regulating, followed by CSF

Interferon (IFN)

Function - three classes - IFN-α and IFN-β are antiviral agents - IFN-γ is a pro-inflammatory agent Source - Virus-infected cells - NK cells - T-lymphocytes Designation - IFN followed by Greek letter

Describe the structure, location, and specific function of five major classes of immunoglobulins

G-MADE IgG - Monomer (one Y-shaped protein) - 75-85% of antibody in blood - Predominant antibody in lymph, CSF, serous fluid, peritoneal fluid - Cross the placenta IgM - Pentamer (composed of five monomers) found mostly in blood - Not versatile in its biological functions - Most effective at causing agglutination of cells + binding complement - Responsible for rejection go mismatched blood transfusions IgA - Typically a dimer (composed of two monomers) - Found in areas exposed to environment - Produced in various secretions - Plays significant role in protecting respiratory and gastrointestinal tract - Helps to prevent pathogens from adhering to epithelial tissue + penetrating underlying tissue through neutralization - Especially effective at agglutination IgD - Monomer that functions as antigen-specific B-lymphocyte receptor - Identifies when B-lymphocytes may be ready for activation to participate in pricing adaptive immunity IgE - Monomer they has very low rate of synthesis - Generally formed in response to allergic reactions + parasitic infections - Causes release of histamine and other mediators

Benefits of inflammatory response

Helping eliminate pathogens by limiting their spread Destroying infectious agents + removing cellular debris Producing conditions for tissue repair + healing

Chemicals of inflammation

Histamine - Vasodilation - Increased permeability of capillaries - Conversion of inactive plasma protein into active peptides - Released early in inflammation - Source: mast cells, basophils, platelets Kinins - Vasodilation + increased permeability of capillaries - Increase production of CAMs - Stimulate sensory pain receptors - Source: plasma protein produced by liver as kininogen, activated by tissue injury Leukotrienes (slow-reacting substance of anaphylaxis [SRS-A]) - Effects similar to histamine - Released layer in inflammatory response than histamine + longer lasting - Source: eicosanoids produced from arachidonic acid molecules of mast cell + basophil plasma membranes Prostaglandins - Vasodilation - Fever - Stimulate sensory pain receptors - Source: eicosanoids produced from arachidonic acid molecules of mast cell + basophil plasma membranes Chemotactic factor - Attracts immune cells - Release of specific factor attract a specific type of cell - Source: mast cells + basophils Serotonin - Effects similar to histamine - Source: platelets Nitric Oxide - Vasodilation - May inhibit mast cells + platelets - Source: endothelium of blood vessels Alpha-1 antitrypsin - Inhibits damage to connective tissue by enzymes released from destroyed phagocytes - Source: plasma protein formed by liver C-reactive protein - Activates complement by binding to polysaccharides on bacteria surface - Source: liver IL-1 and TNF-α - Increase cell-adhesion molecules (CAMs) to cause margination - Cause endothelial cell contraction to facilitate diapedesis - Source: dendritic cells + macrophages

Bacteria

Microscopic, single-celled organisms Composed of prokaryotic cells - Smaller in size (1-2 microm) - Lack a nuclear envelope - DNA/cytoplasm enclosed by plasma membrane + cell wall Sticky polysaccharide capsule - increases virulence (ability to cause serious illness) May have a pill (hairlike structures that act like Velcro for attaching to body structures) Cause disease by releasing enzymes or toxins that interfere with function of cells

Explain why the processes of T-lymphocytes are collectively called the cell-mediated branch of adaptive immunity

Immune response of T-lymphocytes is effective against antigens associated with cells that it is referred to

Explain why T-lymphocytes leaving the thymus are called both immunocompetent and naive

Immunocompetent cells - Able to bind antigen and respond to it Naive T-lymphocyte - T-lymphocytes lack experience because they have not yet encountered the antigen that they recognize

Describe inflammation and discuss the events involved

Inflammation (inflammatory response) - immediate, local, nonspecific event that occurs in vascularized tissue against a great variety of injury-casuing stimuli Steps: 1) Release of various chemicals - Chemicals promote inflammation 2) Vascular changes - Chemicals cause a variety of responses in local blood vessels [vasodilation of arterioles, increase in capillary permeability, stimulation of capillary endothelium for cell-adhesion molecules (CAMs)] 3) Recruitment of leukocytes - Margination - Diapedesis - Chemotaxis 4) Delivery of plasma proteins - Selective plasma proteins brought into injured or infected site (clotting proteins, kinins)

List the benefits of a fever

Inhibits replication of bacteria + viruses Promotes interferon activity Increases activity of lymphocytes Accelerates tissue repair Increases CAMs on endothelium of capillaries in lymph nodes

Discuss the difference between the primary response and the secondary response to antigen exposure

Initial Exposure + Primary Response - Can be in the form of an active infection or a vaccine - Lag or latent phase: period of no detectable antibody in the blood (3-6 days) - Production of antibody: within 1-2 weeks, plasma cells produce IgM and then IgG; antibody titer levels peak and then decrease over time Subsequent Exposures and Secondary Response - Lag or latent phase: much shorter; presence of memory lymphocytes - Production of antibody: antibody levels rise more rapidly with greater proportion of IgG

Compare the primary functions of innate and adaptive immunity

Innate Immunity - Born with specific defenses - Innate immune system: barriers of skin + mucosal membranes that prevent entry and nonspecific internal defenses (immune cells, chemicals, physiologic processes - Structures/mechanisms do not require previous exposure fo a foreign substance + respond immediately to any potential harmful agent Adaptive Immunity (Acquired immunity/ Specific immunity) - Actions of T-lymphocytes and B-lymphocytes exclusively - Responds to a specific lifetime

Protozoans

Microscopic, unicellular eukaryotic organisms - Lack a cell wall Spread bu mosquitoes - Enters the blood where it infects erythrocytes, casting destruction

Other secretions

Lacrimal fluid - Fluid produced by lacrimal glands; contains lysozyme and IgA - Washes microbes away from surface of eyes; contains antimicrobial agents Cerumen - Waxy secretions within external auditory meatus - Waterproofs external auditory meatus; may trap microbes in external ear

Secretions produced by skin and mucous membrane

Lysozyme - Antibacterial enzyme - Attacks cell wall of some bacteria (gram positive bacteria) Defensins - Small proteins - Form pores in plasma membrane of microbes; compromising their structural integrity Dermicidin - Small proteins produced by skin - Antibacterial agent against both gram positive and gram negative bacteria; antifungal agent Immunoglobin A (IgA) - Specific type of antibody present in areas exposed to environment - Binds with specific foreign substance (antigen)

Explain the process of MHC class I molecules in nucleated cells and MHC class II molecules in professional antigen-presenting cells

MHC Class I - Glycoproteins - Genetically determined and unique to each individual - Continuously synthesized by RER and embedded into plasma membrane to display endogenous proteins (endogenous pathway) MHC Class II - Glycoprotein - Continuously synthesized by RER and embedded into plasma membrane to engulf exogenous antigens (exogenous pathway)

What do monocytes become when they leave the blood and travel to the site of an infection.

Macrophages

Chemotaxis

Migration of cells along a chemical gradient Helps account for increase in leukocyte count that occurs during an active infection

Multicellular parasites

Nonmicroscopic organisms (larger than cm in size) Reside within a host from which they take nourishment

Viruses

Not cells Very small (1/100 of a microm) Composed of DNA or RNA within a protein capsid (shell) Obligate intracellular parasites - must enter a cell to replicate Process includes directing the infected cell to synthesize copies of both viral DNA or RNA molecule + its capsid protein New viral particles are then formed within infected cells + released to enter surrounding cells Kills the cells it invades Cause different diseases depending upon the type go cell they infect

Apoptosis-Initiating Cells

NK (natural killer) cells - Destroy wide variety of unhealthy/unwanted cells through apoptosis - Cells eliminated include virus-infected cells, bacteria-infected cells, tumor cells, cells of transplanted tissue - Patrol the body in an effort to detect unhealthy cells (immune surveillance) - Destroy unhealthy cells by release of cytotoxic chemicals (perforin, granzymes)

Respiratory tract

Nasal secretions - Contain lysosome, defensins, and IgA - Contain antimicrobial substances Vibrissae - Hairs in nasal cavity - Trap microbes in nose Cilia - Extensions of plasma membrane - Sweep mucus in respiratory tract so that it can be expectorated or swallowed Coughing and sneezing - Blasts of expired air - Mechanical elimination of microbes or other foreign substances from respiratory tract

Effects of inflammation

Net movement of additional fluid from blood through infected or injured area, and then into lymph Exudate (fluid + cellular/protein mix) delivers immune cells and substances needed to eliminate the injurious agent and promote healing Increase in fluid due to: - Vasodilation: allows more blood into infected area - Increased capillary permeability: endothelial cells lining blood vessel wall contract causes larger openings, allowing more fluid to move from blood to IF - Loss of plasma protein: decreases capillary osmotic pressure, resulting in less fluid being retained in blood + reabsorbed back into blood during capillary exchange

Which leukocyte is most prevalent in blood?

Neutrophils

Phagocytic Cells

Neutrophils, Macrophages, Dendritic cells - Engulf unwanted substances such as infectious agents and cellular debris through phagocytosis Vesicle formed merges with a lysosome to form a phagolysosome Macrophages and dendritic cells continue to follow phagocytosis - Present fragments of microbe on their cell surface to T-lymphocytes (antigen presentation) - Necessary for initiating adaptive immunity

Events of a fever

Onset - Hypothalamus stimulates blood vessels in dermis of skin to vasoconstriction to decrease heat loss through a skin - Person may experience chills (heat loss) Stadium - Elevated temperature is maintained - Metabolic rate increases to promote physiologic processes - Liver + spleen bind zinc + iron to slow microbial reproduction Defervescence - Temperature returns to normal set point - Happens when hypothalamus is no longer stimulated by pyrogens, prostaglandin release decreases, and temp set point reverts to normal - Hypothalamus stimulates mechanisms to release heat from the body - Person may appear flushed and skin warm to touch

Describe the four major means by which complement participates in providing innate immunity

Opsonization - binding of a protein to a portion of bacteria or other cell type that enhances phagocytosis - Opsonin: binding protein; functions as a red flag to indicate tagged microbe Inflammation - complement increase inflammatory response through activation of mast cells + basophils and by attracting neutrophils + macrophages Cytolysis - various complement components trigger direct killing of a target by forming protein channel in plasma membrane - Membrane attack complex (MAC) Elimination of immune complexes - complement links immune (antigen-antibody) complexes to erythrocytes so they may be transported to liver and spleen - Erythrocytes stripped of complexes by macrophages within organs

Which of the following statements is true regarding memory in humoral immunity? Memory lasts longer in humoral immunity than in cellular immunity. Memory B-lymphocytes attack the antigen directly without the need fo form plasma cells. Memory B-lymphocytes are found mainly in the lymph nodes. Plasma cells form within hours in primary exposure, creating a response so rapid that no noticeable signs of illness appear. When memory B-lymphocytes attack an antigen, it is called the "primary response".

Plasma cells form within hours in primary exposure, creating a response so rapid that no noticeable signs of illness appear.

Describe the function of plasma cells in the effector response of B-lymphocytes

Plasma cells remain in lymph nodes, continuing to synthesize + release antibodies

Place the events of lymphocyte maturation in the correct sequence.

Primary lymphocyte structures produce lymphocytes. Pre-T-lymphocytes Lymphocytes mature in primary lymphatic structures Naive immunocompetent T-lymphocytes Lymphocytes migrate and are housed in secondary lymphatic structures Lymphocytes proliferate and are activated T-lymphocytes carry out effector functions Foreign antigens are eliminated

What is the correct sequence of endogenous antigen presentation?

Proteins are broken into fragments, transported to the rough ER, and combined with class I MHCs, move to the Golgi apparatus, and then to the plasma membrane

Describe lymphocyte recirculation, and explain its general function

Provides a means of delivering different lymphocytes to secondary lymphatic structures

Describe receptors of both T-lymphocytes and B-lymphocytes

T-lymphocyte - T-cell receptor (TCR) - Helper T-lymphocytes contain TCRs + CD4 proteins - Cytotoxic T-lymphocytes contain TCRs + CD8 protein B-lymphocyte - B-cell receptor (BCR)

Explain how an unhealthy cell is destroyed by cytotoxic T-lymphocytes

T-lymphocytes activated + memory cytotoxic T-lymphocytes also leave secondary lymphatic structure Migrate to site of infection in body's tissue Cytotoxic T-lymphocytes destroy unhealthy or infected cells that display antigen

Why might it be beneficial to allow a mild fever to continue? Select all that apply: Replication of bacteria and viruses is slowed. Interferon activity is depressed. It stimulates migration of immune cells into the tissues. It accelerates tissue repair.

Replication of bacteria and viruses is slowed. It stimulates migration of immune cells into the tissues. It accelerates tissue repair.

Gastrointestinal Tract

Saliva - Secretions released into mouth from salivary glands; contain lysosome and IgA - Help wash away microbes; contains antimicrobial substances Hydrochloric acid (HCL) - Strong acid produced with stomach - Creates very low pH (~2) that destroys many bacteria, bacterial toxins, and other microbes that enter stomach Defecation and vomiting - Removal of waste from GI tract - Eliminate microbes before they can be absorbed into blood

Where can the types of leukocytes of the immune system be found

Secondary lymphatic system - T-lymphocytes and B-lymphocytes - Housed in structures of lymph nodes, spleen, tonsils, lymphatic nodules, MALT Select organs - Macrophages - May be permanent residents (fixed macrophages) or migrate through tissues (wandering macrophages) Epithelial layers of skin + mucosal membranes - Dendritic cells - Engulf pathogens in skin and mucosal membranes + migrate to lymph node through lymph vessels that drain tissue Connective tissue - Mast cells - Especially abundant in dermis of skin + mucosal Lin sings of respiratory, GI, urinary, reproductive tracts - Also housed in connective tissue organs (endomysium that ensheathes muscle fibers)

Explain how T-lymphocytes mature

T-lymphocytes originate in red bone marrow + migrate to thymus to complete maturation Thymocytes (pre-T-lymphocytes) migrate from red bone marrow to thymus Possess unique TCR receptor Thymocytes produced through "gene shuffling" T-lymphocyte must have its TCR tested to determine nit only whether it is able to bind to MHC molecule

List the physical, chemical, and biological barriers to entry of harmful agents of the body

Skin Mucous membranes Respiratory tract GI tract Urogenital tract Skin + Mucous membranes Other secretions

Prions

Small fragments of infectious proteins Cause disease in nervous tissue Ex. "Bovine Spongiform Encephalopathy" or "Mad Cow Disease - Spread from cows to humans by consuming infected meat - Nerves within muscle are contaminated with prions

Cytokines

Small, soluble proteins produced by cells of both innate + adaptive immune system Regulate + facilitate immune system activity 1) Serve as a means of communication between cells 2) Control development + behavior of immune cells 3) Regulate inflammatory response of innate immune system 4) Function as weapons to destroy cells Released from one cell and binds to a specific receptor of a target cell - Action similar to a hormone Have a short half-life Different categories: - Interleukin (IL) - Tumor necrosis factor (TNF) - Colony-stimulating factor (CSF) - Interferon (IFN)

Describe the formation and function of T-lymphocytes (Tregs) in peripheral tolerance

Subclass of CD4 cells called regulatory T-lymphocytes (Tregs) - Formed from T-lymphocytes that bind self-antigens to a moderate extent compared to other CD4+ cells - Function in self-tolerance outside the primary lymphatic structures (peripheral tolerance)

Determine the features of an antigen, and explain what is meant by antigenic determinant

Substance that binds to a component of the adaptive immunity system (T-lymphocyte or antibody) Foreign antigens (nonself-antigens) - bind with body's immune components because they are different enough in structure from human body's molecules - Self-antigens - body's molecules; don't bind with the body's immune components Antigenic determinant (epitope) - specific site on antigen molecule that is recognized by lymphocytes (and antibodies)

Discuss how happens stimulate immune response

Substance that is too small to function as an antigen alone, but when attached to a carrier molecule in the host, becomes antigenic and triggers an immune response Accounts for hypersensitivity reactions to drugs (penicillin) and chemicals in environment (pollen)

Compare the activation of B-lymphocytes with that of T-lymphocytes

T-lymphocytes require two signals B-lymphocytes do not require antigen to be presented by other nonlymphocyte cells - Recognize/respond to antigens outside pf cells First signal - Antigen binds to BCR and antigen cross-links BCRs - Stimulated B-lymphocyte engulfs, processes, presents antigen to helper T-lymphocyte that recognizes antigen Second signal - Occurs when activated helper T-lymphocyte releases IL-4 to stimulate B-lymphocyte - Activation of B-lymphocytes causes B-lymphocytes to proliferate + differentiate - Most of activated B-lymphocytes differentiate into plasma cells that produce antibodies, and remainder become memory

Eosinophils

Target multicellular parasites, attacking organisms' surfaces Mechanism of destruction - include degranulation + release of enzymes Release proteins that form a transmembrane pore to destroy cells of multicellular organism Immune response associated with allergy and asthma Innate immune cells possess "pattern recognition receptors" on cell surfaces

Compare and contrast positive and negative selection of T-lymphocytes and what is meant by central tolerance

Thymic selection Positive selection - Occurs within outer cortex of thymus - TCR in plasma membrane of T-lymphocyte must be able to recognize and bind MHC molecule - Thymocytes that can bine an MHC molecule survive, and those that cannot are eliminated Thymocytes migrate into medulla for negative selection Negative selection - Cells must not bind to any self antigens that are presented within MHC molecule - Tested by thymic dendritic cells presenting self-antigens - If thymocyte does not bind, then it is destroyed - Cells learn to "ignore" molecules of the body or self-antigens (self tolerance) - This process that occurs primarily in lymphatic structures is more specifically called central tolerance Thymocytes that survive both positive and negative selection can bind an MHC molecule + recognize foreign antigen - Only ~2% survive Differentiation - Thymocyte into either a helper T-lymphocyte (CD4 cell) by selective loss of CD8 protein or cytotoxic T-lymphocyte (CD8 cell) by selective loss of CD4 protein

T or F: A helper T-lymphocyte must become activated before it can stimulate a B-lymphocytes to produce antibody.

True

T or F: Interferon may induce the degradation of viral RNA or DNA and inhibits the synthesis of viral proteins.

True

Urogenital tract

Urine - Formed in kidneys and is transported out of the body through urinary tract - Flow of urine flushes microbes from urinary tract Lactate - Weak acid - Produced by vagina - Creates low pH that slows of prevents growth of microbes

Describe the general structure of an immunoglobulin molecule, including its two functional regions

Y-shaped, soluble protein composed of four polypeptide chains Variable regions - Located at ends of "arms" of antibody contain at antigen-binding site - Most antibodies have two antigen-binding sites - Variable region binds antigen through weak intermolecular forces Constant region - Contains Fc region, which is the portion of antibody that determines biological functions of antibody - Five major classes of immunoglobulins: IgG, IgM, IgA, IgD, IgE

Once activated, helper T-lymphocytes ________

continue to release cytokines such as IL-2.

A hypersensitivity reaction occurs __________.

during a second or subsequent exposure to antigen.

T-lymphocytes that have not yet been exposed to specific foreign antigen are called ______ T-lymphocytes.

naive

Antibodies are ___________ produced in response to an antigen.

proteins