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Anatomy 2 Ch5

Lymphatic system and other immune stuff

QuestionAnswer
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
Created by: Devtemrys
 

 



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