BIOL 2402 Unit #2 Lecture Exam - Ch. 22 The Lymphatic System & Immunity
Name the three main lines of defense and give an example of each:
1) Innate external defences (surface barriers): Skin and mucous membranes; coating in secretions like mucus & tears 2) Innate internal defenses: Cells and chemicals in body fluids ready to attack & destroy anything identified as foe 3) Adaptive defenses: consist of T and B cells, takes time to mobilize
List and describe the body's innate (non-specific) defenses.
1) physical barriers: keep hazards outside body 2) phagocytes: engulf pathogens & cell debris 3) immune surveillance: destruction of abnormal cells by NK cells in peripheral tissue 4) interferons: chemical messengers that coordinate defense against viral infections 5) complement system: circulating proteins that assist antibodies in the destruction of pathogens; also lyses cells & enhances phagocytosis & inflammation 6) inflammation: localized tissue-level re: that tends to limit the spread of injury or infection 7) fever: elevation of temp. speeds up tissue metabolism & activity of defense
Compare and contrast the effects of complement with those of interferon.
*interferon interferes w/ viral replication inside virus-infected cells by triggering the production of antiviral proteins *complement activation can rupture the target cell by forming a membrane attack complex (MAC); it also enhances phagocytosis (oponization) & inflammation - interferons are small proteins released by cells infected w/ viruses & trigger the production of antiviral proteins, which interfere w/ the viral replication inside the cell; IFN's are cytokines, which are chemical messengers released by tissue cells to coordinate activities - complement sys is made up of at least 30 complement proteins, which interact w/ each other in cascades to destroy target cell walls, enhance phagocytosis (opsonization), or stimulate inflammation; can be activated by either the classic pathway, lectin pathway, or alternative pathway
IgM class of antibody
- 1st class of antibody secreted after an antigen is encountered - concentration declines as IgG production accelerates - although plasma cells secrete individual IgM molecules, it circulates as a five-antibody starburst - the anti-A & anti-B antibodies responsible for agglutination of incompatible blood types are IgM - may also attack bacteria that are insensitive to IgG
IgD class of antibody
- an individual molecule on surfaces of B cells where it can bind to antigens in the extracellular fluid - binding plays a role in the sensitization of the B cell involved
Structure of antibodies
- antibodies are structural proteins; binding of an antibody to its target antigen starts a chain reaction that leads to the destruction of the target compound or organism - the Y-shaped antibody molecule consists of 2 pairs of poly-peptide chains: 1 pair of heavy chains (form base) & 1 pair of light chains; each chain contains both constant segments & variable segments *B cells produce only 5 types of constant segments; basis for 5 classes of immunoglobulins (Igs) **acronym = MADGE
IgE class of antibody
- attaches as an individual molecule to exposed surface of basophils & mast cells - when suitable antigen is bound by IgE, the cell is stimulated to release histamine & others chemicals that accelerate inflammation in immediate area - also important in allergic responses
IgA class of antibody
- found primarily in glandular secretion (mucus, tears, saliva & semen) - attack pathogens before they gain access to internal tissues - circulate in the blood as individual molecules or in pairs - epithelial cells absorb them f/ the blood & attach a secretory piece, which confers solubility, before secreting the IgA molecules onto the epithelial surface
Explain the difference between cell-mediated (cellular) immunity and antibody mediated (humoral) immunity.
- in cell-mediated (cellular) immunity, T cells defend against abnormal cells and pathogens inside cells. - in antibody-mediated (humoral) immunity, B cells secrete antibodies that defend against antigens and pathogens in body fluids
IgG class of antibody
- largest & most diverse - account for 80% of all antibodies - responsible for resistance against many viruses, bacteria, & bacterial toxins - can cross the placenta - maternal IgG provides passive immunity to fetus - anti-Rh antibodies produced by Rh-negative mothers are also IgG antibodies that cause hemolytic disease of the newborn
What is antigen-presentation and why is it important?
- occurs when an antigen-glycoprotein combination appears in the plasma membrane of an antigen-presenting cell (typically a macrophage or dendritic cell) - T cells sensitive to this combination are activated if they contact the membrane of the antigen-presenting cell
How does a cytotoxic T cell destroy another cell displaying antigens bound to Class I MHC proteins?
- rupturing the target cell's plasma membrane - by stimulating lymphotoxin secretion - or by activating genes in the nucleus that program cell death (apoptosis)
What class of antibody (immunoglobulin) can be shared in the breast milk?
IgA is found in colostrum & breast milk, forms a protective coating in the gastrointestinal tract of a nursing infant
What class of antibody (immunoglobulin) can be shared by a mother with her fetus across the placental membrane?
IgG is the only antibody class that significantly crosses the human placenta
Collections of secondary lymphoid tissue (called ______________ for short) are distributed throughout the mucosal surfaces of the digestive, respiratory, and genitourinary system. Aside from the diffuse cells in respiratory and other mucosa, this includes the following specific structures: a._________________________ (protection of oral and nasal cavities) b._________________________ (first part of the large intestine) c._________________________ (distal portion of the small intestine)
MALT for short a) tonsils b) appendix c) Peyer's patches of small intestine
The _______ proteins are one major class of self-antigens. Thus, before an organ transplant, the donor's and the recipient's ________ proteins are matched as closely as possible.
MHC MHC proteins
A phagocyte recognizes and binds to molecules found on pathogens using special membrane receptors, such as the ______________ receptor and the ______________ (____) receptor.
Mannose receptor Toll-like (TLR) receptor
______________ cells are a type of lymphocyte, but, unlike the B and T cells, they are not specific. However, they can still recognize abnormal cells. T cells look for the presence of abnormal antigens on the cell surface, while these cells look for the ______________ of normally occurring self-proteins.
Natural killer cells are a type of lymphocyte look for the absence of normally occuring "self" proteins
What causes a cell to secrete interferons?
viruses must enter cells to replicate; the presence of the virus replicating inside causes the cell to produce & secrete interferons
Many pathogens have evolved strategies to avoid being killed by phagocytes. For example, some bacteria enclose themselves in capsules. ______________ is a process of coating bacteria to enhance phagocytosis by a macrophage. Phagocytes have receptors that can attach to opsonins on the bacteria. Two factors can act as opsonins: 1. _________________________ 2. _________________________
Opsonization 1. antibodies 2. complement
Activation of the Complement System (Describe the seven functions of antibodies)
when an antibody molecule binds to an antigen, portions of the antibody molecule change shape; this exposes areas that bind complement proteins; the bound complement molecules activate the complement sys, which destroys the antigen
Precipitation & Agglutination (Describe the seven functions of antibodies)
Precipitation - soluble antigens & the binded antibodies become insoluble & precipitate Agglutination - bacteria are bonded through their antigens into a clump
Explain the difference between a primary & secondary immune response.
Primary immune response occurs when an antigen comes in contact to the immune system for the 1st time; the immune system has to learn to recognize antigen & how to make antibody against it, & eventually produce memory lymphocytes. - Responding cell is naïve B-cell and T-cell - Lag phase is often longer (4-7 days), sometimes as long as weeks or months - Level of antibody reaches peak in 7 to 10 days - takes longer time to establish immunity - Amount of antibody produced depends on nature of antigen. Usually produced in low amount - Antibody level declines rapidly - Affinity of antibody is lower for its antigen - appears mainly in the lymph nodes and spleen Secondary immune response occurs when the 2nd time (or more) the person is exposed to the same antigen, immunological memory has been established & the immune system can start making antibodies immediately - Responding cell is memory cell - Lag phase is shorter (1-4 days) due to the presence of memory cell - Level of antibody reaches peak in 3 to 5 days - takes shorter time to establish immunity - Usually 100-1000 times more antibodies are produced - Antibody level remain high for longer period - Antibodies have greater affinity for antigen - appears mainly in the bone marrow, followed by the spleen and lymph nodes
Functions of the spleen include: Removes___________? Stores _______________? Site for activation of the______________?
Removes pathogens, aged erythrocytes & platelets f/ the blood Stores platelets & breakdown products of erythrocytes Provides a site for the interaction of lymphocytes with antigens
Describe the events of a cell-mediated (cellular) immune response.
Responds to intracellular pathogens and abnormal body cells -Function of T-Lymphocytes -Primary defense against intracellular pathogens (also effective eukaryotic extracellular pathogens) Effector of Cell Mediated Response - Cytotoxic T Cells (CD-8) (t-lymphocytes) most common intracellular pathogens are viruses but the response is also effective against cancer cells, intracellular protozoa, and intracellular bacteria. Step 1: Internal cell infection is displayed on the cell surface by MHC class I (antigen-presentation) Step 2: MHC class I molecules bind to cytotoxic T cells Step 3: Costimulation occurs with helper T cells and CD8 Step 4: T cells are activated, proliferate, & differentiate Step 5: Some T cells differentiate into cytotoxic T cells Step 6: Cytotoxic T cells lyse cells and produce cytokines Step 7: Cytokines kill the cell Step 8: Memory T cells form Step 9: Memory T cells remember the antigen and produce faster immune response during subsequent exposures
The ______________ cleanses the blood like the lymph nodes cleanse the lymph.
Spleen
How would a blockage of the thoracic duct affect lymph circulation?
would impair the drainage of lymph f/ inferior to the diaphragm & f/ the left side of the head & thorax, slowing the return of lymph to the venous blood & promoting the accumulation of fluid in the limbs (lymphedema)
Certain _______ (from the adaptive defense system) can enhance the killing process within a macrophage. This only happens when the macrophage presents antigens from the bacteria to this cell. This is an example of the interaction between the innate and adaptive defense systems.
T cells
If the thymus failed to produce thymic hormones, which population of lymphocytes would be affected?
T cells (would drastically reduce the population of T lymphocytes by preventing their differentiation f/ lymphoid stem cells)
Describe the events of an antibody-mediated (humoral) immune response.
The primary function of the humoral, or antibody-mediated, immune response is to control freely circulating pathogens Extracellular antigen & class II MHC proteins (indicates presence of pathogens, toxins, or foreign proteins) ↓ CD4 T cells ↓ - Memory T cells await appearance of antigen) - Helper T cells stimulate immune response by T cells & B cells ↓ Activation of B cell → produces memory B cells ↓ - Production of plasma cell ↓ secretion of Antibodies - destruction of antigens
Opsonization (Describe the seven functions of antibodies)
a coating of antibodies & complement proteins increases the effectiveness of phagocytosis; some bacteria have slick plasma membranes or capsules, but opsonization makes it easier for phagocytes to hold on before engulfing & phagocytes can bind more easily to antibodies & complement proteins than they bare surface of a pathogen
This defense mechanism (named in question 6 as humoral immunity) identifies enemies by recognizing ______________ unique to the pathogens. When they are overwhelmed, they secrete _________________________ to mobilize the adaptive defenses.
a limited number of markers chemical messengers
A rise in the level of interferon in the body suggests what kind of infection?
a viral infection Interferon does not prevent viruses f/ entering the cell, but "interferes" with the virus's ability to replicate in the cell, slow the spread of infection to other cells.
Unlike class I MHC proteins, which can be displayed on any nucleated cell, class II MHC proteins are displayed only on select cells. Name the antigen-presenting cells that have class II MHC proteins: a. _________________________ b. _________________________ c. _________________________ These cells communicate with CD4 cells, which will become ______________ cells. Antigens presented on class II cells are ______________ antigens.
a) dendritic cells b) macrophages c) B cells which will become helper T cells exogenous antigens (extracellular)
The complement system is a cascade of interdependent proteins that enhances both the innate and adaptive defenses. When activated, these proteins can: a.______________________________________________ b._____________________________________________ c.______________________________________________
a) mark cells for phagocytosis b) promote inflammation c) kill some bacteria all by themselves
While ______________ lymphatic vessels carry lymph from the tissues to the lymph nodes, ______________ vessels carry cleansed lymph away from the lymph nodes.
afferent vessels carry lymph f/ tissue to lymph nodes efferent vessels carry cleansed lymph away f/ the lymph nodes
Neutralization (Describe the seven functions of antibodies)
antibodies cover the toxic site of the antigen; both viruses & bacterial toxins have specific sites that must bind to target regions on cells before they can enter or injure those cells; antibodies may bind to those sites, making the virus or toxin incapable of attaching itself to a cells
Prevention of Bacterial & Viral Adhesion (Describe the seven functions of antibodies)
antibodies dissolved in saliva, mucus, & perspiration coat epithelia, adding an additional layer of defense; that covering makes it difficult for pathogens to attach to & penetrate body surfaces
Stimulation of Inflammation (Describe the seven functions of antibodies)
antibodies may promote inflammation by stimulating basophils & mast cells
B and T lymphocytes recognize pathogens by binding to them. What the lymphocyte recognizes is called the ______________ found on the antigen.
antigenic determinant formed by an antigen (simply referred to as antigen)
Attraction of Phagocytes (Describe the seven functions of antibodies)
antigens covered w/ antibodies attract eosinophils, neutrophils, & macrophages; these cells phagocytize pathogens & destroy foreign or abnormal plasma membranes
Define Pathogen
any disease-causing organism a virus, bacteria, fungus, or parasite, that can survive & even thrive in the body
Primary lymphoid organs, where B and T cells originate & mature, are the bone marrow and thymus. The B cells mature in the ______________.
bone marrow
NK cells kill like ______________ T cells; direct contact with a target cell causes it to undergo ______________, a form of cellular suicide.
cytotoxic T cells apoptosis (programmed cell death)
Why do lymph nodes enlarge during some infections?
enlargement results f/ an increase in the # of lymphocytes & phagocytes in the node called "swollen glands" or "lymphadenitis"
How does the formation of an antigen-antibody complex cause the elimination of an antigen?
formation of an antigen-antibody complex eliminates antigens by neutralization; by agglutination & precipitation; by activating complement; by attracting phagocytes; by opsonization; by stimulating inflammation; or by preventing bacterial & viral adhesion
What effects do pyrogens have in the body?
increase body temp. (produce a fever) by stimulating the temp. control area of the preoptic nucleus of the hypothalamus
The interferons secreted by this cell bind to receptors on nearby cells, causing these nearby cells to produce proteins that ______________ by degrading ______________ and preventing synthesis of ______________.
inhibit viral replication viral RNA viral proteins
When the surface barriers (innate external defenses) are penetrated, what is the next line of defense?
innate internal defenses
What is the major histocompatibility complex (MHC) and why is it important?
is a group of genes that code for human leukocyte antigens - abnormal peptides in the cytoplasm of a cell can become attached to MHC proteins & then be displayed on the cell's plasma membrane; the recognition of such displayed peptides by T cells can initiate an immune response
The lymph is filtered through the _______ _______, where antigens and pathogens are removed and the immune system can be activated.
lymph nodes
Secondary lymphoid organs, where lymphocytes become activated, include the following structures: a._________________________ b._________________________ c._________________________ d._________________________ e._________________________
lymph nodes spleen Peyer's patches in the s. intestine appendix tonsils
List the components of the lymphatic system and describe their functions.
lymph: interstitial fluid in lymphatic vessels lymphatic vessels: carry lymph f/ peripheral tissues to venous system up to the body's trunk to lymphatic trunk (then to thoracic duct & right lymphatic duct) lymphatic capillaries: branch through peripheral tissues; lined w/ endothelial cells & permits fluid & solutes (including proteins) viruses, bacteria, & cell debris to enter primary lymphoid tissues & organs (red bone marrow & thymus): where lymphocytes form & mature secondary lymphoid tissues & organs (tonsils, MALT, lymph nodes, appendix & spleen): where lymphocytes activate & clone lymphoid cells (lymphocytes & others): consist of immune system cells found in lymphoid tissues; function in defense; i.e. phagocytes & lymphocytes
What type of cells would be affected by a decrease in the number of monocytes forming cells in red bone marrow?
macrophages of all types including Kupffer cells of the liver, dendritic (Langerhans) cells in the skin & digestive tract, and alveolar macrophages.
Primary lymphoid organs, where B & T cells originate & mature, are the bone marrow & thymus. The T cells mature in the ______________. (Hint: This is how they came to be called B & T cells.)
mature in the thymus
Explain the difference between nonspecific defense and specific defense.
nonspecific (innate) immunity: - born with it - does not distinguish 1 threat f/ another Ex: skin as physical barrier, phagocytes specific (adaptive) immunity: - respond to specific antigens & organize a defense against that particular type - protects against further attacks by the same type of pathogen - develops after birth after exposure to antigens Ex: T cells & B cells
Specific B cells called ______________ cells secrete ______________, which bind to the antigens.
plasma cells secrete antibodies, which bind to the antigens.
What are the functions of natural killer cells?
responsible for recognizing & destroying abnormal cells when they appear in peripheral tissues; their continuous "policing" of peripheral tissues is called "immune surveillance"
Class II MHCs are produced in the _________________________ and pick up the exogenous antigens when they fuse with the ______________.
rough endoplasmic reticulum phagolysosome
Name three circumstances in which T cells would be activated against body cells: 1. _________________________ 2. _________________________ 3. _________________________
1. a cell has become cancerous 2. a cell has been invaded by a virus 3. a cell has been transplanted by another individual
Name two results of presenting the exogenous antigen on class II MHC proteins: 1. CD4 cells are converted to helper T cells when ______________ cells and ______________ present the antigen. 2. ______________ cells and ______________ present antigens to helper T cells to request further activation.
1. dendritic cells and macrophages 2. B cells and macrophages
Name two functions of the lymph nodes: 1. _________________________ 2._________________________
1. filter the lymph by removing antigens & other debris 2. provide sites for the activation of B and T cells by antigens, which generate the immune response
At least 10 different TLRs have been identified on human phagocytes. Two reactions are triggered when TLRs recognize a pathogen: 1. _________________________ 2. _________________________
1. ingestion of the pathogen 2. release of chemical alarm signals that mobilize other cells of innate & adaptive immunity
Interferons that are cytokines that do the following three things: 1. _________________________ 2. _________________________ 3. _________________________
1. interfere w/ viral replication 2. modulate inflammation 3. activate immune cells
Name the two types of antimicrobial proteins: 1. _________________________ 2. _________________________
1. interferons 2. compliment system
Once the surface barrier has been broken, the second line of defense, the innate internal defense system (nonspecific defense system), attempts to limit the spread of pathogens. Name the five components of the innate internal defense system: 1. _________________________ 2. _________________________ 3. _________________________ 4. _________________________ 5. _________________________
1. phagocytic cells - neutrophils & phagocytes 2. natural killer (NK) cells - kill body cells that have become virus-infected or cancerous 3. antimicrobial proteins - complement & interferons 4. inflammation 5. fever
Identify the two forms of active immunity and the two forms of passive immunity. Give one example of each type of immunity.
2 forms of active immunity (develops after exposure to an antigen) - naturally acquired active immunity (getting the chicken-pox) - artificially acquired active immunity (chicken-pox vaccine) 2 forms of passive immunity (antibodies transferred f/ another source) - naturally acquired passive immunity (transfer of antibodies f/ the placenta or in breast milk) - artificially acquired passive immunity (person contracts rabies & is given an injection containing antibodies against the virus)
List the four general properties of adaptive immunity.
specificity = ability to respond to a particular disease (occurs b/c T cells & B cells re: to the molecular structure of specific antigens) versatility = to confront any antigen at any time (based on the large diversity of lymphocytes in the body & f/ variability in the structure of synthesized antibodies) memory = to remember an antigen so that it responds faster & stronger the next time its exposed to that antigen (memory cells enable the immune sys to remember previous target antigens) tolerance = to ignore "self" antigens & only target "non-self" or foreign antigens (ability of the immune sys to ignore some antigens, such as those of normal body cells)
Primary lymphoid organs, where B & T cells originate & mature, are the bone marrow & thymus. Both B and T cells originate from ______________.
stem cells in the bone marrow
______ cells are found in the germinal centers of the lymphoid follicles, and ______ cells wander through the deep ______________, searching dendritic cells for their special antigen.
B cells T cells deep cortex
What are CD proteins?
CD proteins (cluster of differentiation) are markers on T cell plasma membranes whether a T cell responds to antigens held in class I or class II MHC proteins depends on the structure of the T cell plasma membrane -CD3 markers are present on all T cells -CD8 makers are on cytotoxic & regulatory T cells - one type of CD8 responds quickly to a class I MHC-bound antigen, giving rise to larger #'s of cytotoxic T cells & memory T cells - other types of CD8 cell responds more slowly, giving rise to small #'s of regulatory T cells -CD4 markers are on all helper T cells
Define autoimmune disease/disorder
the immune response inappropriately targets normal body cells & tissues An individual develops antibodies of their own cells - antibodies attach to self antigens & begin attacking the individual's tissues - inflammation as well as tissue necrosis occurs. - - can be general or systemic
______________ immunity is directed against pathogens within the cells (intracellular). This immunity involves ____ lymphocytes.
Cellular immunity T cells (lymphocytes)
______________ cells circulate through the body searching for infected or cancerous cells by examining the antigenic determinant on ______________ MHC proteins on the cell surface. Fragments of ______________, degraded proteins are loaded onto these proteins in the endoplasmic reticulum. If the antigenic peptide is a/an ______________ antigen, the body cell will be destroyed.
Cytotoxic T cells class I MHC proteins endogenous antigens (intracellular) foreign antigen
The ______________, a primary lymphoid organ, is the site for differentiation of lymphocytes into mature T cells. What happens to this organ as we age?
thymus as we age, the relative size & function gradually decreases; replaced by fat cells & fibrous connective tissue, called thymic atrophy causing the elderly to be more susceptible to infection
What is the difference between a helper T cell and a cytotoxic T cell?
Helper T(TH) cells: stimulate responses of both T cells & B cells, vital to the immune response, b/c they must activate B cells before the B cells can produce antibodies - in response to extracellular pathogen - recognizes antigens MHC class II - carries CD4 marker - helps or induce immune response - APC's are activated to kill intracellular microorganisms by secreting cytokines Cytotoxic T (Tc) cells: responsible for cell-mediated immunity, these cells enter peripheral tissues & directly attack antigens physically & chemically - in response to intracellular pathogen - recognizes antigens MHC class I - carries CD8 marker - primarily cytotoxic - destroys virus infected or tumor cells directly
(Question #6) ____________ immunity is directed against pathogens in the extracellular fluid. This immunity involves _______ lymphocytes.
Humoral immunity B cells (lymphocytes)
Which type of immunity involves antibodies?
Humoral immunity Cellular immunity does not