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Anatomy 2 Ch5
Lymphatic system and other immune stuff
Question | Answer |
---|---|
resistance | The ability to ward off the pathogens that produce disease |
susceptibility | Lack of resistance |
Nonspecific resistance to disease | includes defense mechanisms that provide general protection against invasion by a wide range of pathogens. |
Immunity involves | activation of specific lymphocytes that combat a particular pathogen or other foreign substance. |
Lymphatic system consists of | Fluid called lymph flowing within lymphatic vessels, several structures and organs that contain lymphatic tissue, and bone marrow, which is the site of lymphocyte production |
Interstitial fluid and lymph are very similar. Their major difference is | location. |
The lymphatic system functions | Draining interstitial fluid–Returning leaked plasma proteins to the blood–Protecting against invasion by nonspecific defenses and specific immune responses. |
Capillaries that begin as closed-ended tubes found in spaces between cells... | Combine to form lymphatic vessels |
Fluid flows through | lymph nodes towards large veins above the heart |
Lymphatic capillaries structure is designed to let tissue fluid in but not out,.. | anchoring filaments keep tube from collapsing –overlapping endothelial cells open when tissue pressure is high (one-way valve) |
The passage of lymph | arteries and blood capillaries → interstitial spaces → lymph capillaries →lymphatic vessels → lymph trunks → the thoracic duct or right lymphatic duct → the subclavian veins |
Lymph flows as a result of | the milking action of skeletal muscle contractions and respiratory movements. It is also aided by lymphatic vessel valves that prevent backflow of lymph. |
Flow of lymph | Fluid & proteins escaping from vascular capillaries is collected by lymphatic capillaries & returned to the blood. Respiratory & muscular pumps promote flow of lymphatic fluid |
Lymphatic vessels empty into | subclavian veins |
Primary lymphatic organs provide environment for | stem cells to divide & mature into B and T lymphocytes |
red bone marrow gives rise to | mature B cells |
thymus is site where | pre-T cells from red marrow mature |
Secondary lymphatic organs & tissues are the site where most immune responses occur | lymph nodes, spleen & lymphatic nodules |
Lymph node structure | Encapsulated oval structures located along lymphatic vessels. Contain T cells, macrophages, follicular dendritic cells, and B cells. |
Lymph enters nodes and is | filtered to remove damaged cells and microorganisms before it exits. |
Foreign substances filtered by the lymph nodes are trapped by | nodal reticular fibers |
Lymph nodes are the site of proliferation of | plasma cells and T cells. |
Flow in lymph node is | unidirectional |
afferent vessels | lead in lymph node |
sinuses lead to | efferent vessels that exit at hilus |
What filters lymph? | Only nodes |
Thymus gland | Large organ in infants (70 g) but atrophied as adult (3 g)•2 lobed organ located in mediastinum•Each lobule has cortex &medulla |
Cortex of thymus gland | tightly packed lymphocytes ¯ophages |
Medulla of thymus gland | reticular epithelial cells produces thymic hormones |
Spleen | 5 inch organ between located between stomach & diaphragm |
Parenchyma consists of | white pulp and red pulp |
white pulp is | lymphatic tissue (lymphocytes & macrophages) around branches of splenic artery–Macrophages remove worn-out or defective RBCs, WBCs, and platelets |
red pulp is | venous sinuses filled with blood & splenic tissue (splenic cords) |
Mechanical protection | includes the intact epidermis layer of the skin , mucous membranes, the lacrimal apparatus, saliva, mucus, cilia, the epiglottis, and the flow of urine. |
Chemical protection | localized on the skin, in loose connective tissue, and stomach. |
Lysozyme is | an enzyme component of sweat that also has antimicrobial properties. |
mucous membrane secretes viscous mucous | cilia and mucus trap and move microbes toward throat |
second line of defense | involves internal antimicrobial proteins, phagocytic and natural killer cells, inflammation, and fever. |
Antimicrobial proteins discourage microbial growth | interferons–complement proteins–transferrins |
Body cells infected with viruses produce proteins called | interferons (IFNs) |
Once produced and released from virus-infected cells, IFN | diffuses to uninfected neighboring cells and binds to surface receptors, inducing uninfected cells to synthesize antiviral proteins that interfere with or inhibit viral replication. |
INFs also | enhance the activity of phagocytes and natural killer (NK) cells, inhibit cell growth, and suppress tumor formation |
Complement System | group of about 30 proteins present in blood plasma and on cell membranes. these proteins “complement” or enhance certain immune, allergic, and inflammatory reactions. |
Natural killer cells | kill a variety of microbes & tumor cells. found in blood, spleen, lymph nodes & red marrow–attack cells displaying abnormal MHC antigens |
Phagocytes (neutrophils & macrophages) | fixed macrophages stand guard in specific tissues•wandering macrophages in most tissue |
Phagocytosis 5 stages | Chemontaxis, adherence, ingestion, digestion, killing |
Chemotaxis | attraction to chemicals from damaged tissues, complement proteins, or microbial products |
Adherence | attachment to plasma membrane of phagocyte |
Ingestion | engulf by pseudopods to form phagosome |
Digestion & killing | merge with lysosome containing digestive enzymes & form lethal oxidants exocytosis residual body |
Signs of inflammation | redness, heat, swelling, pain, Loss of function may be a fifth symptom, depending on the site and extent of the injury. |
Function of inflammation | is to trap microbes, toxins or foreign material & begin tissue repair |
Fever | Abnormally high body temperature that occurs because the hypothalamic thermostat is reset•Occurs during infection & inflammation |
The trigger of fever | bacterial toxins trigger release of fever-causing cytokines such as interleukin-1 |
Benefits of fever | intensifies effects of interferons, inhibits bacterial growth, speeds up tissue repair–Aspirin prevents interleukin-1 synthesis–Liver sequesters iron |
Immunity differs from nonspecific defense mechanisms | specificity, memory |
specificity | recognize self & non-self |
memory | 2nd encounter produces even more vigorous response |
Antigens | substances recognized as foreign by the immune responses. |
Both T cells and B cells derive from | stem cells in bone marrow |
Before T cells leave the thymus or B cells leave bone marrow, they acquire | several distinctive surface proteins; some function as antigen receptors, molecules capable of recognizing specific antigens |
T cell mature in thymus | cell-mediated response•killer cells attack antigens•helper cells costimulate T and B cells -effective against fungi, viruses, parasites, cancer, and tissue transplants |
B cells in bone marrow | antibody-mediated response•plasma cells form antibodies–effective against bacteria |
Cell-mediated immunity(CMI) | refers to destruction of antigens by T cells. –CMI always involves cells attacking cells. |
Cell-mediated immunity particularly effective against | intracellular pathogens, such as fungi, parasites, and viruses; some cancer cells; and foreign tissue transplants. |
Antibody-mediated (humoral) immunity (AMI) | refers to destruction of antigens by antibodies. Works mainly against antigens dissolved in body fluids and extracellular pathogens, primarily bacteria, that multiply in body fluids but rarely enter body cells. |
Epitope | The part of a macromolecule that is recognized by the immune system |
Required characteristics to be considered an antigen | immunogenicity, reactivity |
immunogenicity | ability to provoke immune response |
reactivity | ability to react to cells or antibodies it caused to be formed |
If antigen get past the bodies nonspecific defenses | enter the bloodstream to be deposited in spleen–penetrate the skin & end up in lymph nodes–penetrate mucous membrane & lodge in associated lymphoid tissue |
Hapten | smaller substance that cannot trigger an immuneresponse unless attached to larger protein (lipid of poison ivy) |
Explanation for great diversity of receptors is | genetic recombination of few hundred small gene segments |
Each B or T cell has its own unique set of | gene segments that codes its unique antigen receptor in the cell membrane |
human leukocyte antigen (HLA) | integral membrane proteins |
MHC-I molecules | built into cell membrane of all cells except red blood cells |
if cell is infected with virus... | MHC-I contain bits of virus marking cell so T cells recognize is problem |
MHC-II markers | seen only on membrane of antigen presenting cells (macrophages, B cells, thymus cells) |
if antigen presenting cells (macrophages or B cells) ingest foreign proteins | they will display as part of their MHC-II |
B cells can bind to | antigen in extracellular fluid |
T cells can only | recognize fragments of antigens that have been processed and presented to them as part of a MHC molecule• |
Helper T cells | “see” antigens if part of MHC-II molecules on surface of antigen presenting cell |
Cytotoxic T cells | “see” antigens if part of MHC-I molecules on surface of body cells |
antigen-presenting cells (APCs) | process exogenousantigens (antigens formed outside the body) and present them together with MHC class II molecules to T cells. |
APCs include | macrophages, B cells, and dendritic cells. |
Foreign antigen in body fluid is phagocytized by APC | macrophage, B cell, dendritic cell |
bound to MHC-II molecules stuck into antigen presenting cell membrane | |
APC migrates to | lymphatic tissue to find T cells |
Endogenous antigens are synthesized within the body and include | viral proteins or proteins produced by cancer cells |
Fragments of endogenous antigen are associated with | MHCI molecules inside the cell. |
The antigen MHCI complex | moves to the cell’s surface where it alerts T cells. |
Cytokine | Small protein hormones involved in immune responses–secreted by lymphocytes and antigen presenting cells |
Cytokine therapy uses cytokines (interferon) | alpha-interferon used to treat Kaposi’s sarcoma, genital herpes, hepatitis B and C & some leukemias–beta-interferon used to treat multiple sclerosis–interleukin-2 used to treat cancer (side effects) |
In a cell-mediated immune response | an antigen is recognized (bound), small number of specific T cells proliferate&differentiate into a clone of effector cells (population of identical cells that can recognize same antigen&carry out some aspect of immune attack), &antigen is eliminated. |
Activation, of Cytotoxic T Cells | Receptor on CD8 cell binds to foreign antigen fragment part of MHC-I•Costimulation from helper T cell–prevents accidental immune response |
Proliferation & Differentiation of Cytotoxic T Cells | Proliferates & differentiates into population (clone) of Tc cells and memory Tc cells•Occurs in secondary lymphatic organs such as lymph node |
Activation of Helper T Cells | Receptor on CD4 cell binds to foreign antigen fragment associated with MHC-II•Costimulation with interleukin |
Proliferation & Differentiation of Helper T Cells | Proliferates & differentiates into population (clone) of TH cells and long-lived memory TH cells |
Mature T Cells Helper T cells names | Helper T (TH) cells, or T4 cells |
Mature T Cells Cytotoxic T cell names | Cytotoxic T (TC) cells, or T8 cells |
Mature T cells Memory T cells | Memory T cells (TM) |
Helper T Cells | Display CD4 on surface so also known as T4 cells or THcells•Recognize antigen fragments associated with MHC-II molecules & activated by APCs•Function is to costimulate all other lymphocytes |
autocrine function of Helper T Cells | costimulates itself to proliferate and secrete more interleukin (positive feedback effect causes formation of many more helper T cells) |
Cytotoxic T Cells | Display CD8 on surface•Known as T8 or Tc or killer T cells•Recognize antigen fragments associated with MHC-I molecules |
Memory T Cells | T cells from a clone that did not turn into cytotoxic T cells during a cell-mediated response•Available for swift response if a 2nd exposure should occur |
Cytotoxic T cells fight | foreign invaders by killing the target cell without damaging the cytotoxic T cell itself |
When cytotoxic T cells encounter a cell displaying a microbial antigen | they can release granzymes which trigger apoptosis. The microbe is then destroyed by phagocytes. |
infected cells and release perforin and granulysin. Perforin causes cytolysis while granulysin destroys the microbe. | |
Cytotoxic T cells can also release | lymphotoxin which activates damaging enzymes within the target cell. |
When the cytotoxic T cell detaches from a target cell | it can destroy another cell. |
Immunological surveillance is carried out by | cytotoxic T cells. |
Success of a proposed organ or tissue transplant depends on | histocompatibility. Tissue typing (histocompatibility testing) is done before any organ transplant. |
Surveillance = | |
B cells sit still and let antigens be brought to them | stay put in lymph nodes, spleen or peyer’s patches |
Once activated the B cells | differentiate into plasma cells that secrete antibodies |
Antibodies circulate in lymph and blood | combines with epitope on antigen like how a key fits a specific lock |
Some activated B cells become | antibody-secretion plasma cells. Others become memory B cells. |
Activation of B Cells | B cell receptors bind to antigen -- response more intense if on APC•Helper T cell costimulates |
Proliferation, & Differentiation | Rapid cell division & differentiation occurs- long-lived memory cells, clone of plasma cells. |
B cells can produce | antibody at 2000 molecules/sec for 4-5 days•secrete only one kind of antibody |
Antibodies Definition | A protein that can combine specifically with the antigenic determinant on the antigen that triggered its production. |
Antibody structure | They have a heavy and light chains and variable and constant portions |
Immunoglobulins in order | IgG, IgA, IgM, IgD, IgE |
Antibody Actions | Neutralization of antigen by blocking effects of toxins/preventing its attachment to body cells•Immobilize bacteria•Agglutinate & precipitate antigens by cross-linking them•Activate Complement system•Enhance phagocytosis through precipitation |
Primary immune response | first exposure to antigen response is steady, slow–memory cells may remain for decades |
Secondary immune response with 2nd exposure | 1000’s of memory cells proliferate & differentiate into plasma cells & cytotoxic T cells•antibody titer is measure of memory (amount serum antibody)–recognition & removal occurs so quickly not even sick |