2Functions of Lymphatic System Draining interstitial fluidTransporting dietary lipidsProtection
3Lymphatic VesselsBegin as closed ended lymph capillaries in tissue spaces between cellsNOT A CIRCULATING FLUIDInterstitial fluid drains into lymphatic capillaries, forming lymph.Lymph capillaries merge to form lymphatic vessels
4and finally back to the vascular system. Lymphatic vessels carry lymph into and out of lymph nodesand finally back to the vascular system.
7Lymphatic capillaries Made of a single layer of squamous epithelial cellsSlightly larger than blood capillariesCells overlap and act as one-way valvesOpened by pressure of interstitial fluidAnchoring filaments attach cells to surrounding tissue
12Lymphatic vessels join to form lymphatic trunks. Lymphatic trunks join to form :Thoracic duct (3/4 of body)Right lymphatic duct (drains right arm, and right side of head, neck and upper torso)These empty into subclavian veins at junction with internal jugular vein.
14Formation of lymph:Fluid leaves capillaries by diffusion and filtrationEscaped proteinsIf lymph flow blocked = tissue swelling or edemaSpecialized lymphatic capillaries in vili of small intestine transport lipids - they are called lacteals, and the fluid is called chyle.
15Lymphatic Organs Red bone marrow Primary organs Thymus gland Lymph nodesLymph nodules Secondary organsSpleen
17Lymph Nodes Lymph is filtered through lymph nodes Found in clusters “Waste water treatment plants”Vary in sizePrincipal groupings in cervical, axillary and inguinal regions.Provide biological filtrationSite of cancer growth and metastasis
20Vessels enter node on convex side Lymph passes through irregular channels called sinusesLeaves node through one or two efferent vessels at the hilum or hilusCapsule, cortex and medullaCortex contains lymph nodulesFollicular dendritic cellsGerminal centers – B cells proliferate
23Lymph nodules are also found singly or in groups throughout the mucous membranes of the respiratory, urinary, reproductive and digestive tracts.MALT – mucosa associated lymphoid tissuePeyer’s patches in ileumTonsilsSome in appendix
24Tonsils – lymphoid tissue under the mucous membranes of the throat palatine tonsilspharyngeal tonsil – adenoidlingual tonsilsFirst line of defenseTonsillectomy
26Thymus gland in mediastinum above the heart largest at age then begins to atrophyPre - T cells come from bone marrow and develop into T cellsT cells then go to other lymphatic tissuesThymus produces hormone thymosin - aids maturation of T cells elsewhere in body
33White pulp:little islands, mostly B cellsRed pulp:Venous sinusesSplenic cords – RBCs, macrophages, lymphocytes, plasma cells and granulocytes
34Functions of Spleen Blood formation – Blood filtration Blood storage All blood cells in fetusOnly lymphocytes and monocytes after birthBlood filtrationRemoves bacteria, particles, worn out RBCs and platelets (recycles iron)Blood storageCan contain over one pint of blood
35Nonspecific Resistance The ability to ward off disease is called resistance.Lack of resistance is susceptibility.Nonspecific resistance refers to a wide variety of body responses against a wide range of pathogens. A pathogen is any microorganism that causes disease.
36ImmunityImmunity involves activation of specific lymphocytes to combat a specific foreign agent.
37Nonspecific Resistance Species (Inborn) Resistance – certain species contract certain diseases, while other species do not.
38Mechanical Barriers Skin and mucous membranes : First line of defense Physical barrierShedding of dead cellsMucusHairsCiliaCoughing and sneezing, production of tears, saliva, urine, defecation and vomiting physically remove harmful substances
39Chemical ProtectionSebaceous glands produce sebum – fatty acids inhibit growth of bacteria and fungiLactic acid further decreases skin pHAccumulation of saltVaginal secretions are also slightly acidicGastric juice – acid, enzymes and mucusLysozyme in tears, perspiration, saliva and tissue fluids
40Normal Microbiota – bacteria living on skin inhibit the growth of pathogens by producing antibiotics
41Antimicrobial Substances Transferrins are proteins that tie up the free iron in the blood and interstitial fluid.Interferon – “Paul Revere Chemical” – a glycoprotein produced by virus infected cells that cause neighboring cells to produce anti-viral proteins. These also enhance phagocytosis and can suppress growth of tumor cells.
42The Complement System: normally inactive proteinsWhen activated, they “complement” or enhance certain immune, allergic and inflammatory reactions.Activation of inflammationOpsonization – enhances phagocytosisCytolysis – membrane attack complex
43Fever :Causes liver and spleen to sequester ironIncreases phagocytosisInhibits growth of microbesSpeeds up body repair
44Inflammation:Characterized by:Heat, swelling, redness, and pain(and sometimes loss of function)calor, tumor, rubor and dolor
45Stages of inflammation Vasodilation and increased permeability of blood vesselsPhagocyte migrationNeutrophils come firstFollowed by macrophagesTissue Repair
47Natural Killer Cells Next line of defense (with phagocytes) Lymphocytes – but do not respond to specific antigensCan kill a variety of microbes plus tumor cells.May release perforins, or attack directlyCell may not display correct MHC antigens
48ImmunitySpecific resistance to disease involving the production of a specific lymphocyte or antibody against a specific antigen.An antigen is any substance that elicits an immune response. Best antigens are:LargeComplexRecognized as foreign
49Haptens are molecules that are small, foreign and complex Haptens are molecules that are small, foreign and complex. To elicit an immune response, they must piggy-back on a larger molecule, often blood proteins.Epitopes: a foreign protein may result in several different antibodies. Each antibody recognizes a different portion of the protein. These regions are called epitopes.
50Two forms of immunity:Humoral or antibody mediated immunityB cells (mature in bone) make antibodies: specific proteins that bind to specific antigensORCell-mediated immunityTcytoxic lymphocytes attack virus infected or tumor cells directly
52“The Story” Macrophage destroys a bacterium Takes bacterial antigen and fuses it with MHC II complexMHC II complex and antigen are placed on cell membrane.Displays antigen (like a proud cat) – so it is called an antigen presenting cell.
53It shows antigen to helper T cells, until it finds one that has a receptor that matches the antigen complex.The helper T cell binds to the antigen complex, and the macrophage is stimulated to produce the cytokine Interleukin -1A cytokine is a protein hormone which regulates normal cell functions, like growth and differentiation.
54Every step needs 2 signals to proceed. IL-1 binds to receptors on the helper T cell, causing helper T-cell to clone itself and produce IL-2.IL-2 causes lymphocytes to multiply.These steps are common to both humoral and cell-mediated immunity.
55Humoral or Antibody mediated immunity In order for B cells to become activated and make antibodies against an antigen, two things must happen:B cell must encounter the antigenIL-2 produced by helper T cell must be present.
56When both signals are present (the antigen and IL-2) When both signals are present (the antigen and IL-2). The B cell becomes activated and forms two types of cells: plasma cells and memory cells.Plasma cells produce large quantities of their specific antibody into the blood.Memory cells lie in wait for the next infection.
62The first antibodies produced are IgM The first antibodies produced are IgM. Pentamers – with ten combining sites – very effective in opsonization and activating complementSeveral days later, IgG is produced – single unit antibodies, abundant in serum, cross the placenta, and have the longest half-life.
63Cell mediated immunity A virus is a core of nucleic acid wrapped in a protein.To reproduce, it must make use of a host cell to replicate the viral nucleic acids and proteins and assemble new viruses.
64Infected cells put viral proteins on their membranes. This antigen is processed by macrophages.Antibodies can’t get at viruses inside a cell, so we need something different : a Tcytotoxic or Tc Cell.The Tc encounters the viral antigen with the MHC -1 complex on the infected cell.
65Now needs the second stimulus – IL-2 from the helper T cell. Tc cell clones itself, and makes activated Tc cells and memory cells.Tc Cells bind to antigens on infected cells and release:Perforins – punch holes in cell membrane.Lymphotoxins- activate the cell’s own self-destruct mechanism
66Tc Cells are effective against bacteria which are intracellular parasites, viruses, fungi, cancer cells associated with viral infections, and transplanted cells.
67Immune ResponseThe first time you encounter an antigen, you have few B cells or Tc cells against that antigen = primary responseThe next time, you have many memory cells, so response is much quicker, so you don’t come down with the disease = secondary response
69HIV/AIDS Human immunodeficiency virus Attacks helper T cells Without production of IL-2, there is no second signal, and humoral and cell mediated immunity are shut off. See increase in rare diseases:TB, Kaposi sarcoma, etc.
72Delayed Hypersensitivity A type of cell mediated immunity.Td cell – requires usual two signalsSecond time antigen is encountered, Td cell produces several cytokines that attract and activate macrophages, resulting in an inflammatory reaction.Examples: poison ivy (urushiol), TB skin test
73Immediate Type Hypersensitivity Exposure to certain antigens (allergens) results in the formation of IgE antibodiesIgE antibodies bind to mast cells by the Fc end.When the antigen is encountered again, binding with the antibody causes mast cell to release histamine granules.
76May be able to desensitize individual by giving allergen to stimulate IgG antibodies. These tie up antigen before they can bind with IgE.
77Acquired immunity Active = person makes own antibodies Passive = person receives antibodies from someone elseNatural = “just happens”Artificial = caused by man (often using a needle)
78Natural active acquired immunity: person comes down with measlesArtificial active acquired immunity:person is immunized with a vaccineArtificial passive acquired immunity:Person receives serum with antibodiesNatural passive acquired immunity:Baby receives antibodies with mother’s milk - colostrum