Lymphatic System and Lymphatic System and Immunity:Immunity:

Lymphatic SystemLymphatic System

LymphLymph Lymphatic vesselsLymphatic vessels Lymphatic tissueLymphatic tissue Lymphatic nodulesLymphatic nodules Lymph nodesLymph nodes TonsilsTonsils SpleenSpleen ThymusThymus

Lymphatic VesselsLymphatic Vessels

Carry lymph away from tissuesCarry lymph away from tissues Lymphatic capillariesLymphatic capillaries

More permeable than blood capillariesMore permeable than blood capillaries Epithelium functions as series of one-way valvesEpithelium functions as series of one-way valves

Functions of the Functions of the Lymphatic SystemLymphatic System

Fluid balanceFluid balance Excess interstitial fluid enters Excess interstitial fluid enters

lymphatic capillaries and becomes lymphatic capillaries and becomes lymphlymph

Fat absorptionFat absorption Absorption of fat and other Absorption of fat and other

substances from digestive tractsubstances from digestive tract DefenseDefense

Microorganisms and other foreign Microorganisms and other foreign substances are filtered from lymph by substances are filtered from lymph by lymph nodes and from blood by spleenlymph nodes and from blood by spleen

Lymphatic VesselsLymphatic Vessels

Carry lymph away from tissuesCarry lymph away from tissues Lymphatic capillariesLymphatic capillaries

More permeable than blood capillariesMore permeable than blood capillaries Epithelium functions as series of one-way valvesEpithelium functions as series of one-way valves

Lymphatic VesselsLymphatic Vessels Lymphatic capillaries join to formLymphatic capillaries join to form Lymphatic vesselsLymphatic vessels

Have valves that ensure one-way flowHave valves that ensure one-way flow Lymph nodes: Distributed along Lymph nodes: Distributed along

vessels and filter lymphvessels and filter lymph Lymphatic trunks: Jugular, Lymphatic trunks: Jugular,

subclavian, bronchomediastinal, subclavian, bronchomediastinal, intestinal, lumbar intestinal, lumbar

Lymphatic ducts: Right and thoracic Lymphatic ducts: Right and thoracic which connect to large veins which connect to large veins

Lymph Drainage Into Lymph Drainage Into VeinsVeins

Lymphatic Tissue and Lymphatic Tissue and NodulesNodules

Lymphatic tissueLymphatic tissue Consists mainly of Consists mainly of

lymphocyteslymphocytes Encapsulated or notEncapsulated or not

Lymphatic nodulesLymphatic nodules Numerous in loose Numerous in loose

connective tissue of connective tissue of digestive (Peyer’s digestive (Peyer’s patches), patches), respiratory, urinary, respiratory, urinary, reproductive reproductive systemssystems

TonsilsTonsils

Large groups of Large groups of lymphatic nodules in lymphatic nodules in nasopharynx and oral nasopharynx and oral cavitycavity

Provide protection Provide protection against bacteria and against bacteria and other harmful materialother harmful material

GroupsGroups PalatinePalatine PharyngealPharyngeal LingualLingual

Lymph NodesLymph Nodes

Organized in cortex and medullaOrganized in cortex and medulla Substances removed by phagocytosis or Substances removed by phagocytosis or

stimulate lymphocytes or bothstimulate lymphocytes or both Only structures to filter lymphOnly structures to filter lymph

Afferent and efferent vesselsAfferent and efferent vessels

SpleenSpleen Located in left superior side of abdomenLocated in left superior side of abdomen

Can be ruptured in traumatic abdominal Can be ruptured in traumatic abdominal injuries resulting in bleeding, shock, deathinjuries resulting in bleeding, shock, death

Blood flows through at 3 different ratesBlood flows through at 3 different rates Fast (most), slow, intermediateFast (most), slow, intermediate

FunctionsFunctions Destroys defective RBCsDestroys defective RBCs Detects and responds to foreign substancesDetects and responds to foreign substances Limited reservoir for bloodLimited reservoir for blood

SpleenSpleen

ThymusThymus

Located in superior mediastinumLocated in superior mediastinum Divisions: Cortex and medullaDivisions: Cortex and medulla Site of maturation of T cellsSite of maturation of T cells

ImmunityImmunity Ability to resist damage from foreign Ability to resist damage from foreign

substances as microorganisms and harmful substances as microorganisms and harmful chemicalschemicals

CategoriesCategories Innate or nonspecific resistanceInnate or nonspecific resistance

Mechanical mechanisms: Prevent entry or remove microbesMechanical mechanisms: Prevent entry or remove microbes Chemical mediators: Promote phagocytosis and Chemical mediators: Promote phagocytosis and

inflammationinflammation Cells: Involved in phagocytosis and production of chemicals Cells: Involved in phagocytosis and production of chemicals

Adaptive or specific immunityAdaptive or specific immunity Specificity: Ability to recognize a particular substanceSpecificity: Ability to recognize a particular substance Memory: Ability to remember previous encounters with a Memory: Ability to remember previous encounters with a

particular substance and respond rapidlyparticular substance and respond rapidly

Innate immunityInnate immunity

Inflammatory ResponseInflammatory Response Tissue injury regardless of type can cause Tissue injury regardless of type can cause

inflammationinflammation Response initiated by chemical mediators Response initiated by chemical mediators

that produce vasodilation, chemotactic that produce vasodilation, chemotactic attraction, increased vascular attraction, increased vascular permeabilitypermeability

TypesTypes Local: Symptoms are redness, heat, swelling, Local: Symptoms are redness, heat, swelling,

pain, loss of functionpain, loss of function Systemic: Symptoms are increase in Systemic: Symptoms are increase in

neutrophil numbers, fever and shockneutrophil numbers, fever and shock

Inflammatory ResponseInflammatory Response

Normal Microcirculation FlowNormal Microcirculation Flow

Exudate FormationExudate Formation

Leukocyte Margination and MigrationLeukocyte Margination and Migration

DiapedesisDiapedesis

ChemotaxisChemotaxis

Innate Immunity: CellsInnate Immunity: Cells White blood cellsWhite blood cells

Most important Most important cellular cellular components of components of immune systemimmune system

MethodsMethods ChemotaxisChemotaxis Phagocytosis Phagocytosis

NeutrophilsNeutrophils Phagocytic and Phagocytic and

first cells to enter first cells to enter infected tissueinfected tissue

MacrophagesMacrophages Monocytes that leave Monocytes that leave

blood, enter tissuesblood, enter tissues Large phagocytic cellsLarge phagocytic cells

Basophils and mast Basophils and mast cellscells Promote inflammationPromote inflammation

EosinophilsEosinophils Reduce inflammationReduce inflammation

Natural killer cellsNatural killer cells Lyse tumor and virus-Lyse tumor and virus-

infected cellsinfected cells

Antigenic DeterminantsAntigenic Determinants

Antigenic Antigenic determinants determinants Specific regions of a Specific regions of a

given antigen given antigen recognized by a recognized by a lymphocytelymphocyte

Antigenic receptorsAntigenic receptors Surface of lymphocyte Surface of lymphocyte

that combines with that combines with antigenic determinantantigenic determinant

C3a stimulates mast cells and basophils, which then secrete inflammatory mediators

Adaptive ImmunityAdaptive Immunity

Involves the ability to recognize, respond Involves the ability to recognize, respond to, and remember a particular substanceto, and remember a particular substance

StimulantsStimulants Antigens: Large moleculesAntigens: Large molecules

Foreign: Not produced by body, introduced from Foreign: Not produced by body, introduced from outsideoutside

Self-antigens: Produced by bodySelf-antigens: Produced by body Haptens: Small molecules and capable of Haptens: Small molecules and capable of

combiningcombining TypesTypes

Humoral or Antibody-mediated: B cellsHumoral or Antibody-mediated: B cells Cell-mediated: T cellsCell-mediated: T cells

Origin and Origin and DevelopmentDevelopment

of Lymphocytesof Lymphocytes B and T cellsB and T cells

Originate in red Originate in red bone marrowbone marrow

Move to lymphatic Move to lymphatic tissue from tissue from processing sites processing sites and continually and continually circulatecirculate

Clones are small Clones are small groups of identical groups of identical lymphocyteslymphocytes

Origin and Origin and DevelopmentDevelopment

of Lymphocytesof Lymphocytes Positive selectionPositive selection

Ensures survival of lymphocytes that react Ensures survival of lymphocytes that react against antigensagainst antigens

Negative selectionNegative selection Eliminates lymphocytes that react against self-Eliminates lymphocytes that react against self-

antigensantigens Primary lymphatic organs Primary lymphatic organs (red bone marrow, (red bone marrow,

thymus)thymus) Where lymphocytes mature into functional cellsWhere lymphocytes mature into functional cells

Secondary lymphatic organsSecondary lymphatic organs Where lymphocytes produce an immune Where lymphocytes produce an immune

responseresponse

Major Major Histocompatability Histocompatability

Complex (MHC)Complex (MHC) Most lymphocyte activation involves Most lymphocyte activation involves

glycoproteins of cell surfaces called glycoproteins of cell surfaces called MHC moleculesMHC molecules Class I molecules display antigens on Class I molecules display antigens on

surface of nucleated cells, resulting in surface of nucleated cells, resulting in destruction of cellsdestruction of cells

Class II molecules display antigens on Class II molecules display antigens on surface of antigen-presenting cells, surface of antigen-presenting cells, resulting in activation of immune cellsresulting in activation of immune cells

Antigen ProcessingAntigen Processing

MHC class IMHC class I

PhagocytosisPhagocytosis Phagocytosis also involves Phagocytosis also involves

membrane invagination.membrane invagination. This process does not involve This process does not involve

clathrin.clathrin. Pseudopods extend around a Pseudopods extend around a

particle, forming a particle, forming a phagosome.phagosome.

Phagosome will fuse with a Phagosome will fuse with a lysosome, containing digestive lysosome, containing digestive enzymes.enzymes.

There are smaller transport There are smaller transport mechanisms in the wall of the mechanisms in the wall of the secondary lysosome.secondary lysosome.

CostimulationCostimulation

Proliferation of Helper Proliferation of Helper T CellsT Cells

Proliferation of B CellsProliferation of B Cells

Lymphocyte InhibitionLymphocyte Inhibition

Tolerance: To prevent the immune Tolerance: To prevent the immune system from responding to self-system from responding to self-antigensantigens Provoked byProvoked by

Deletion of self-reactive lymphocytesDeletion of self-reactive lymphocytes Preventing activation of lymphocytesPreventing activation of lymphocytes Activation of suppressor T cellsActivation of suppressor T cells

Antibody-Mediated Antibody-Mediated ImmunityImmunity

Antibodies or Antibodies or Immunoglobulins Immunoglobulins (Ig)(Ig) Classes: IgG, IgM, Classes: IgG, IgM,

IgA, IgE, IgDIgA, IgE, IgD StructureStructure

Variable region: Part Variable region: Part that combines with that combines with anitgenic determinant anitgenic determinant of antigenof antigen

Constant region: Constant region: Responsible for Responsible for activitiesactivities

Actions of AntibodiesActions of Antibodies

Antibody ProductionAntibody Production

Cell-Mediated Cell-Mediated ImmunityImmunity

Antigen activates effector T cells and produces Antigen activates effector T cells and produces memory T cellsmemory T cells

Cytotoxic T cells lyse virus-infected cells, tumor Cytotoxic T cells lyse virus-infected cells, tumor cells, and tissue transplantscells, and tissue transplants

Cytotoxic T cells produce cytokines, which promote Cytotoxic T cells produce cytokines, which promote phagocytosis and inflammationphagocytosis and inflammation

Interactions and Interactions and Responses ofResponses of

Innate and Adaptive Innate and Adaptive ImmunityImmunity

Ways to Acquire Ways to Acquire Adaptive ImmunityAdaptive Immunity

Effects of AgingEffects of Aging

Little effect on lymphatic systemLittle effect on lymphatic system Decreased ability of helper T cells to Decreased ability of helper T cells to

proliferate in response to antigensproliferate in response to antigens Decreased primary and secondary Decreased primary and secondary

antibody responsesantibody responses Decreased ability of cell-mediated Decreased ability of cell-mediated

immunity to resist intracellular immunity to resist intracellular pathogenspathogens

Immune System Immune System ProblemsProblems

Hypersensitivity reactionsHypersensitivity reactions Autoimmune diseaseAutoimmune disease Severe combined immunodeficiency Severe combined immunodeficiency

disease (SCID)disease (SCID) TransplantationTransplantation

Acute rejectionAcute rejection Chronic rejectionChronic rejection