Chapter 12: The Lymphatic System & Body Defenses

Lymphatic & Immune System Objectives

• Explain how the lymphatic system is functionally related to the cardiovascular & immune systems.• Name the two major types of structures composing the lymphatic system• Describe the source of lymph, and explain its formation and transport• Describe the function(s) of lymph nodes, tonsils, the thymus, Peyer’s patches, and the spleen• Describe the protective functions of skin and mucous membranes• Explain the role of natural killer cells• Describe the inflammatory process• Explain the importance of phagocytes• Name several antimicrobial substances produced by the body that act in innate body defense• Describe how fever helps protect the body• Define antigen & hapten name the substances that act as complete antigens• Name the two arms of the adaptive defense system, and relate each to a specific lymphocyte type (B or T Cell)• Compare the development of B and T Cells• State the roles of B & T Cells• Explain the importance of Antigen Presenting Cells in immunity• Define humoral immunity• State the role of plasma cells• Explain the function(s) of antibodies and describe clinical uses of monoclonal antibodies• Distinguish between active & passive immunity• Describe the structure of an antibody monomer• List the 5 antibody classes, and describe their specific roles in immunity• Describe several ways in which antibodies act against antigens• Distinguish between the roles of helper, regulatory, and cytotoxic T Cells• Describe immunodeficiencies, allergies, and autoimmune diseases

Lymphatic System

• Made up of Lymphatic Vessels & various Lymphoid Tissues & Organs scattered throughout the body.

• Lymphatic Vessels: transport fluids back to the blood• Lymphoid Tissues & Organs: house phagocytic cells &

lymphocytes which defend foreign invaders & create resistance to disease

Lymphatic Vessels

• Interstitial fluid is created as blood circulates and exchanges nutrients, wastes, & gases

• Up to 3L per day becomes interstitial fluid; these fluids need to return to the blood

• Lymphatic vessels pick up the excess tissue fluid, Lymph (clear water) & return it to the blood.

• Lymphatic vessels form a one-way system with valves to flow toward the heart

Lymphatic Vessels

• If interstitial fluid accumulates it is called edema.• Excessive Edema impairs the ability of tissue cells to exchange

fluid

• Proteins, cell debris, cancer cells, bacteria, & viruses, can enter lymphatic capillaries easily

• Lymph is transported from lymph capillaries to lymph vessels (lymphatic collecting vessels), they drain into either the right lymphatic duct (drain from the right arm and the right side of head and thorax) or into the thoracic duct (drain from the rest of the body)

Lymph Nodes

• Lymph Nodes: help protect the body by removing foreign materials such as cancer cells, bacteria, & viruses.

• They produce lymphocytes that start the immune response.• Located in the inguinal, axillary, & cervical regions• Inside of the lymph nodes are:• -Macrophages: engulf and destroy bacteria, viruses, &

other foreign substances• -Lymphocytes: respond to foreign substances

Lymph Nodes

• Lymph Nodes are what get swollen, not glands

• Homeostatic Imbalance:• Nodes become overwhelmed by bacteria, viruses, or cancer cells;

can lead to inflammation can also become secondary cancer sites, they will become swollen but not painful.

Lymphoid Organs

• Spleen: filters blood of bacteria, viruses, and other debris, destroys worn out red blood cells; also site for lymphocyte proliferation & immune system surveillance

• Thymus: programs lymphocytes to carry out protective roles, distinguish between self & foreign matter

• Tonsils: trap & remove any foreign matter

• Peyer’s patches: trap & remove any foreign matter in the small intestine, also found in the appendix

LiverSpleen

Thymus

Thoracic Duct

Lymphatic Vessel

Cervical Nodes

Inguinal nodes

Axillary nodesRight Lymphatic Duct

Cysterna chyli (drainage from digestive organs)

The Immune System

Innate (nonspecific ) defense Mechanisms Adaptive (specific) defense Mechanisms

First line of Defense Second Line of Defense Third Line of Defense

Skin Mucous Membranes Secretions of skin & Mucous Membranes

Phagocytic cells Natural killer cells Antimicrobial proteins The inflammatory response

Lymphocytes Antibodies Macrophages & other antigen-presenting

cells

Immune System

• Innate Defense System: responds immediately to protect the body from all foreign substances

• Adaptive Defense Mechanism: attack against particular foreign substances, must first be exposed to a foreign substance (ANTIGEN) before it can protect the body from an invader

Innate Body Defenses

• Mechanical Barriers that cover the body from invading pathogens (harmful or disease-causing microorganisms)

• Surface Membrane Barriers, First line of Defense:

-Skin: strong physical barrier to most microorganisms

-Mucous membranes: Line all body cavities open to the exterior: digestive, respiratory, urinary,& reproductive tracts

Mucous Membranes

• Mucous membranes provide a variety of protective secretions:• Acidic pH of skin secretions & urine (pH3-5) inhibits bacterial

growth; Vaginal secretions are also acidic• The stomach secretes hydrochloric acid & protein digesting

enzymes; both kill pathogens• Saliva & lacrimal fluid (tears) contain lysozyme (enzyme that

destroys bacteria)• Sticky mucus traps many microorganisms that enter digestive &

respiratory passageways• * Hairs also trap inhaled air sending it to the stomach rather than

the lungs, which provide an ideal site for bacterial growth

Internal Defenses, Second line of Defense

• Phagocytic cells: “eat” foreign particles

• Natural Killer (NK) cells: Lymphocytes that roam the body & kill cancer cells, virus-infected body cells. Act spontaneously against any target by recognizing that they are not “self” cells

-Release Lyse: that attacks the target cell’s membrane by

disintegrating it and then the nucleus of the invader

Inflammatory Response:

• Triggered when body tissues are injured such as from: physical trauma, intense heat, irritating chemicals, infection by viruses & bacteria.

• 4 Common Indicators• -Redness• -Heat• -Swelling• -Pain

Inflammatory Response

Process:1. Cells are injured they release inflammatory chemicals, histamine

& kininsa. cause blood vessels to dilate & capillaries to become leakyb. Activate Pain Receptorsc. Attract phagocytes & other white blood cells

2. Neutrophils respond, squeeze through the capillary walls, gather at the site, & devour foreign material

3. Monocytes (poor phagocytes) turn into Macrophages (excellent phagocytes) within 12 hours

* Severely infected areas form pus: a mixture of dead neutrophils, broken-down tissue cells, & pathogens, if inflammatory responses fail the sac of pus can become walled off, forming an abscess

Second line of Defense

•Phagocytes: located in nearly every body organ, literally means to eat

Ex. Macrophage or neutrophil

Second Line of Defense

• Antimicrobial proteins: enhance the innate defenses either by attacking microorganism directly or by hindering their ability to reproduce.

-Complement Proteins: group of 20 plasma proteins that circulate in the blood in an inactive state

• -Will become attached (fixed) to foreign cells, complement fixation, will create holes in the foreign invader which allow water to rush in and causes the invader to burst

 

*Activated Complement Proteins also amplify the inflammatory response

Second Line of Defense

• Interferon: proteins that attach to healthy cells and interfere with the viruses’ ability to replicate within the healthy cell

• Fever: White blood cells & macrophages secrete “pyrogens” (pyro=fire), causing the body to reset its thermostat to a higher number, make you feel tired & hypersensitive

-Bacteria need a lot of iron & some zinc to multiply, during a

fever the liver & spleen gather up these materials

-Also increases the metabolic rate of tissue cells, speeds up

the repair process

Adaptive Body Defenses

Immune response: Recognizes foreign molecules (antigens) and acts to inactivate or destroy them

1. It is antigen specific: it recognizes & acts against particular pathogens or foreign substances.

2. It is systemic: It goes throughout the body, not just at the initial infection site

3. It has “memory”: it recognizes & mounts an even stronger attack on previously encountered pathogens

Adaptive Body Defenses

•Humoral Immunity: Antibody-mediated immunity, antibodies present in the body’s humors (fluids)

-B Lymphocytes, B Cells produce antibodies & oversee humoral immunity•Cellular Immunity: Cell-mediated immunity when the lymphocytes themselves defend the body

-T Lymphocytes, T Cells non anti-body-producing & overseecellular immunity

•Antigen: any substance capable of mobilizing our immune system; foreign invaders (non-self)•Hapten (incomplete antigen): small molecule that links with our own proteins to cause trouble, poison ivy, animal dander, detergents, hair dyes, cosmetics, etc.

Adaptive Body Defenses

•Lymphocytes: originate in red bone marrow then migrate

-T-Cells arise from lymphocytes that migrate to the thymus,learn self vs. non self

-B-Cells develop in bone marrow

Adaptive Body Defenses

*They both become immunocompetent: capable of responding to a specific antigen by binding to it with antigen-specific receptors that appear on the lymphocyte’s surface, before meeting the antigens they may later attack

*it is our genes, not antigens that determine what specific foreign substances our immune system will be able to recognize & resist

Adaptive Body Defenses

•Antigen-Presenting Cells (APCs): engulf antigens and then present fragments of them to T cells•Major type of APCs: Dendritic cells: Langerhans cells, Macrophages & B lymphocytes– When they present antigens they activate T cells– Activated T Cells release chemicals that make macrophages to

make them insatiable– Macrophages tend to stay in the lymphoid organs– Lymphocytes (B & T cells) circulate continuously through the

body– Dendritic cells have long extensions which make them very

efficient at catching antigens, then travel to the organs to present to T cells

Humoral (Antibody-Mediated) Immune Response

•B lymphocytes are immature until antigens bind to its surface receptors, this sensitizes the lymphocyte to switch on and clone itself, becoming plasma cells•Plasma cells become anti-body producing factories (2000 antibodies/sec) for 4-5 days•B Cells that clone but do not become plasma cells become long-lived memory cells capable of responding to the same antigen at later meetings with it, creating immunological memory•Secondary humoral responses: produce much faster, are more prolonged, and more effective than the events of the primary response

Active vs. Passive Humoral Immunity

•Active Immunity: B cells encounter antigens and produce antibodies against them

•Naturally acquired during bacterial and viral infections

•Artificially acquired when we receive vaccines

Active vs. Passive Humoral Immunity

•Passive Immunity: Antibodies are obtained from the serum of an immune human or animal donor– Your B cells are not challenged by the antigen, immunological

memory does not occur *occurs naturally from mother to fetus & after birth through breast milk*artificially received when a person gets an immune serum or gamma globulin,(produced in another living thing) after exposure to:-Hepatitis-Poisonous snake bites-Botulism-Rabies-Tetanus(These would kill a person before active immunity can be established)

Antibodies:

•Antibodies: immunoglobulins (Igs), soluble proteins secreted by activated B cells or their plasma-cell offspring

•IgD: virtually always attached to B cell, activates the B Cell•IgG: most abundant antibody in blood plasma, only type that can cross the placenta•IgM & IgG: can fix complement•IgA: found mainly in mucus & other secretions•IgE: Involved in allergies (think things are harmful that are not)

Antibody Function

•Complement Fixation: activated when it binds to antibodies, creates holes in the invader, water rushes in and causes the invader to burst•Neutralization: Antibodies bind to the dangerous sites on bacteria & viruses to block the harmful effects•Agglutination: Clump the foreign cells•Precipitation: agglutinated substances become so large & insoluble therefore settle out

Cellular (Cell-Mediated) Immune Response

•*T cells are not able to bind with free antigens like B cells, T cells must be presented by a macrophage •Cytotoxic (killer) T cells: specialize in killing virus-infected, cancer, or foreign graft cells (organ transplants), bind tightly to a foreign cell & release toxic chemicals

• Example of how a virus infects the cell

Cellular (Cell-Mediated) Immune Response

•Helper T cells: Act as directors of the immune system, once activated they circulate through the body & recruit other cells to help fight (Interact directly with B cells, encouraging them to clone)-release cytokine

• 1. Stimulates cytotoxic T cells & B cells to grow and divide• 2. Attract white blood cells such as neutrophils to the area• 3. Enhance the ability of macrophages to engulf & destroy

microorganism

Cellular (Cell-Mediated) Immune Response

•Suppressor T cells: Release chemicals that suppresses the activity of both T & B cells, helps to prevent uncontrolled or unnecessary immune system activity •Memory T cells: remain behind to provide the immunological memory for each antigen encountered and enable the body to respond quickly to subsequent invasions

• Immune System Animation

Organ Transplants & Rejection

1. Autografts tissue grafts transplanted from the same person.2. Isografts tissue grafts from an identical twin.3. Allografts tissue grafts from a person other than an identical twin.

a. At least a 75% match is needed to attempt a graft 4. Xenografts tissue grafts harvested from a different animal species

•After transplant patient receives immunosuppressive therapy in order to kill the rapidly dividing cells such as activated lymphocytes•*Cannot protect the body against other foreign agents while receiving this therapy

Disorders of Immunity

•Homeostatic imbalance: autoimmune diseases, allergies, & immunodeficiencies

Disorders of Immunity

•Autoimmune diseases: person’s own immune system that produces the disorder-Rheumatodi arthritis (RA): systematically destroys joints-Myasthenia gravis: impairs communication between nerves & skeletal muscles-Multiple sclerosis (MS): destroys the white matter (myelin sheaths) of brain and spinal cord-Graves’ disease: Thyroid gland produces excessive amounts of thyroxine-Type 1 Diabetes Mellitus: destroys pancreatic cells resulting in deficient production of insulin-Systemic lupus erythematosus (SLE): occurs mainly in young women, affects the kidneys, heart, lungs, & skin-Glomerulonephritis: impairment of kidney function

Disorders of Immunity

•Allergies (hypersensitivities): abnormally vigorous immune responses in which the immune system causes tissue damage as it fights off a perceived threat that would otherwise be harmless to the body.

Disorders of Immunity, Allergies

•Immediate (acute) hypersensitivity: triggered by the release of a flood of histamine when IgE antibodies bind to mast cells (act with wound healing found close to surface & external environment), causes small blood vessels in the area to become dilated & leaky which causes runny noses, water eyes, and itching.*Occurs within seconds & last about 30 mins

• Anaphylactic Shock (acute): when an allergen directly enters the blood and circulates rapidly through the body, histamine is release however more life threatening because the entire body is involved

•Epinephrine: used to reverse the histamine-mediated effects

Disorders of Immunity, Allergies

•Delayed hypersensitivities: take 1-3 days to appear, activated by cytokines released by activated T cells•Most common:

Allergic contact dermatitis-poison ivy-heavy metals (lead, mercury)-Cosmetics

Disorders of Immunity, Immunodeficiency

•Immunodeficiency: production or function of immune cells or complement is abnormal

-Severe combined immunodeficiency disease (SCID): marked deficit of both B & T cells

-Acquired Immune Deficiency Snydrome: AIDS, cripples the immune system by interfering with the activity of helper T-cells