The Lymphatic System and Body Defenses Death to

The Lymphatic System and Body Defenses: Death to the Invaders!

Lymphatic System Consists of two parts: -the lymphoid vessels - the lymphoid tissue and organs Function: -pick up plasma that has leaked out of blood vessels (called lymph) and return it to the bloodstream through the veins -As nutrient, waste, and gas exchange occurs in the Capillaries up to 3 liters per day of fluid leaks out

Lymph Nodes Lymph is filtered through lymph nodes as it passes back to the bloodstream Lymph nodes contain macrophages and lymphocytes Bacteria, viruses, and foreign materials are destroyed When large numbers of bacteria or viruses are trapped in the node, the node swells and becomes painful

Distribution of Lymph Nodes

Lymphoid Organs

Lymphoid Organs In addition to lymph nodes, the body contains lymphoid organs that play a role in protecting the body However, only lymph nodes filter lymph Lymphoid organs include: Spleen Thymus Tonsils Peyer’s patches

Spleen Filters blood of bacteria, viruses, and other debris Most important function is to destroy worn out red blood cells Also stores platelets and red blood cells It also produces lymphocytes

Thymus, Tonsils, Peyer’s Patches Thymus – found in the thorax superior to the heart Active only in the young Functions in the production of lymphocytes Tonsils – found at the back of the throat Trap and remove bacteria and viruses that enter the throat Peyer’s Patches – found in the small intestine They serve a similar function as do the tonsils

Body Defenses Nonspecific defense system - intact skin and mucous membranes -inflammatory response – rubor, dolor, calor, tumor, and loss of function - These defenses prevent entry and spread of organisms Specific defense system – the immune system - attacks specific invading organisms

The Immune System - attacks specific foreign substances and organisms - most important immune cells are macrophage and lymphocytes - must be exposed to a substance before it can protect against it - produces immunity to diseases

The First Line Of Defense Nonspecific Defenses: Surface Barriers - skin and mucous membranes - Acidic secretions inhibit bacteria - Lysozyme in saliva and tears destroys bacteria - sticky mucous traps organisms - stomach acid kills bacteria

Nonspecific Defenses: Cells - Phagocytes - engulf and destroy invading organisms - They are present in every organ Natural Killer Cells - attack any foreign cell of substance (are nonspecific) - attack the cell’s membrane and destroys the cell

Phagocyte Function

2 nd Line Of Defense Inflammatory Response Pt. 1 - The inflammatory response is considered the second line of defense -injured cells release histamine. Kinins, and other -Inflammatory chemicals. These chamicals: -cause vessels to dilate and capillaries to leak -Activate pain receptors -Attract phagocytes (called chemotaxis)

Inflammatory Response Pt. 2: Three Main Functions - prevent the spread of damaging materials - dispose of cell debris and pathogens - set the stage for repair

Inflammatory Response Pt. 3: Disposal of Debris -Neutrophils enter the inflamed area and begin disposing of damaged / dead cells and pathogens Moncytes enter the area and begin phagocytosis (become macrophages) - Macrophages play a major role in the disposal of debris

Inflammatory Response Pt. 4: Sealing off the area - clotting proteins are activated and seal off the area with fibrin - This prevents the spread of pathogens - fibrin serves as a scaffolding for permanent repair

Inflammatory Response Pt. 5: Conclusion - localized heat speeds up the actions of the inflammatory cells -if the area is invaded by pathogens that have previously invaded the body, the specific immune response attacks the invaders - pus – a collection of dead neutrophils and cell debris - abcess – a walled off sac of pus

Inflammatory Response

Antimicrobial Chemicals -the body produces a number of chemicals that help kill Invading organisms -Complement – a group of 20+ chemicals that circulate in the bloodstream - Interferon – a chemical that protects cells from viral invasion -pyrogens – chemicals that reset the body’s thermostat – causes fever

Complement -attaches to bacteria, fungal, or other foreign cells – this process is called complement fixation - it lyses the cells by damaging the cell membranes - it attracts phagocytes – a process called chemotaxis -it makes foreign cells easier to phagocytize – a process called opsonification

Activation of Complement

Interferon - released by cells that have been invaded by a virus - it binds to the cell membrane of uninvaded cells - it hinders the virus’ ability to invade the cell

Pyrogens -chemicals secreted by WBC’s when they are exposed To invading cells - they cause a fever by resetting the body’s thermostat - fever inhibits bacteria and enhances the inflammatory response

Third Line of Defense Specific Body Defenses: The Immune System - The immune response is the body’s response to specific invaders - it produces immunity (specific protection) to specific invaders - Immunology – the study of immunity -Immunity results in the production of proteins called antibodies that protect the body

Immune Response: Important Aspects -it is antigen specific – it recognizes a particular foreign substance - It is systemic – immunity protects the entire body -It has memory – it recognizes and mounts a stronger attack on previously encountered pathogens – this is known as the “ananestic response” - Immunity has two parts: Humoral – antibodies in the bloodstream Cell – mediated – lymphocytes that attack and destroy

Antigens - Any substance or cell that is foreign to our body - they are large molecules that are normally not in our body -Proteins make the strongest antigens elicit the strongest immune response) - Antigens can be nucleic acids, carbohydrates, or lipids -Small molecules usually are not antigenic – however, they can Bind with our own proteins to produce larger molecules that Are antigenic. The small molecule is called a haptein.

Cells of the Immune System: Overview -B Lymphocytes produce antibodies that produce humoral immunity -T Lymphocytes – various types that attack invading cells in different ways to produce the cell mediated immunity - Macrophages help lymphocytes produce immunity

Humoral Immune Response: Antibody Mediated - Antibodies are proteins that bind to and inactivate antigens - Antibodies are produced by B-Lymphocytes - B-Lymphocytes are activated by binding to an antigen -The activated B-Lymphs divide rapidly to form a colony of many identical cells called clones -The clones then form either plasma cells (produce antibodies) -Or memory cells (produce the ananestic response)

Humoral Response

Plasma Cells and Memory Cells -Plasma cells produce large amounts of antibody levels peak about 10 days after exposure, then he levels fall off -Memory cells remember the antigen and can respond quickly To it again if needed The secondary response is much quicker – antibody levels peak in 2 – 3 days Antibody is produced at a much higher level and remains high for weeks to months

Humoral Response

Active and Passive Humoral Immunity Active Immunity – antibodies produced by contact of B Lymphs with and antigen. There are two types of active Immunity: Natural – immunity produced after exposure to the pathogen Passive – immunity as a result of a vaccine There are two types of vaccine – killed and attenuated (modified live) The term vaccine applies only to viruses

Passive immunity – antibodies against an antigen are given to a patient. These antibodies have been manufactured by another person and given to the patient The patient’s own immune system does not make these antibodies. Passive natural immunity refers to antibodies that are passed from a mother to her child either through the Placenta or through the milk. Passive artificial immunity refers to antibodies that have been given to a patient from a donor.

There are five classes of antibodies Ig. G is the most abundant antibody in the blood plasma It is the main antibody in primary and secondary responses Ig. A is the primary antibody found in the secretions from mucous Membranes – saliva, tears, milk, intestinal lining. It protects mucous membranes from pathogens. Ig. E is secreted by skin and mucous membranes. It is the primary mediator of allergic reactions. Ig. M is found in plasma both free and attached to B lymphs. It serves as an antigen receptor. Ig. D is found in the plasma attached to B lymphs. It serves a role in the activation of B lymphs.

Cell Mediated Immunity T lymphs are activated by antigen that is presented to them in the cell membranes of macrophages. They cannot bind to free antigen. Without “antigen presentation by the macrophage the T lymphs cannot respond to an antigen. Activated T lymphs form several types of “clones – 1. Cytotoxic (killer ) T cells – kill virus infected cells as well as foreign graft cells 2. Helper T cells – they serve as directors of the immune response They stimulate B lymphs to more rapidly produce clones They stimulate antibody production They release lymphokines – chemicals that stimulate both the humoral and cell mediated immune response

3. Suppressor T cells – they lessen the immune response and help bring it to an end. 4. Delayed hypersensitivity T cells – they play a role in delayed allergies and chronic inflammation 5. Memory cells – provide antigenic memory that allows the body to respond more quickly to subsequent exposure

Organ Transplants and Rejection Transplantation of organs or tissue grafts from living or recently deceased donors is a viable treatment option for many patients, including: Kidney failure Heart failure Burn patients Immune rejection presents a major problem for these patients

There are four varieties of tissue grafts Autografts – tissue transplanted from one site to another site on the same person. Isografts – grafts donated by genetically identical individuals i. e. only identical twins Allografts – tissues transplanted from non genetically identical individuals of the same species. Xenografts – tissue grafted from a donor of a different species

Autografts and isografts present no risk of rejection – the tissues of donor and recipient are identical Xenografts are only temporarily successful Due to vast differences in tissue proteins Allografts are often successful. Success is the result of similar tissue antigens. Blood and tissue from donor and recipient must be tested to determine compatibility. Patients are treated with immunosuppressive drugs to prevent rejection.

Immune Deficiencies A defect in the immune system inhibits the body’s ability to defend itself Severe Combined Immunodeficiency Syndrones A group of genetic defects that interfere with both B cell and T cell function. Patients have no defense against disease causing organisms Tx include- bone marrow transplants, protective barriers

Acquired Immune Deficiency Syndrone (AIDS) Destroys the immune system by interfering with helper T cells. AIDS is caused by the human immunodeficiency Virus (HIV

Autoimmune Diseases The body produces antibodies and sensitized T cells that destroy its own tissue. The specific disease produced depends on the target tissue involved. Examples include: Multiple sclerosis – white matter in CNS is destroyed Myasthenia gravis – nerve and muscle communication Graves’ disease – thyroid gland over active Juvenile diabetes – pancreatic beta cells Systemic lupus erythematosus – can affect the kidneys, heart, Lungs, skin Rheumatoid athritis - joints

Hypersensitivities Also called allergies. The body is harmed as the immune System fights a perceived “threat” that is otherwise harmless The term allergen is used to identify this type of antigen. There are two types of allergic reactions – immediate and delayed. Immediate hypersensitivity begin within seconds of contact. Lasts about a half an hour. This reaction is caused by histamine. Can be local or systemic Anaphylactic shock – an ovewhelming, systemic, life threatening reaction

Delayed Hypersensitivity An antibody mediated reaction that develops more slowly – one to three days Examples include: Contact dermatitis Poison ivy