Lymphatic System

The system that keeps us alive and healthy – we call it the immune system.

Pathogens – microorganisms that produce diseases in us. (Bacteria, viruses, fungi, and parasites.

Lymphocytes – The cells of the lymphatic system that respond to ◦ Invading pathogens◦ Abnormal body cells (ex. Cancer)◦ Foreign proteins (ex. Toxins)

Vessels – a network throughout the body Fluid – called lymph Lymphoid Organs – contain a large number

of lymphocytes (example Lymph and spleen)

Methods of organization

T-Cells (thymus-dependent)◦ 80% of all lymphocytes◦ Cytoxic attack foreign and infected cells◦ Helper T-Cells – send a signal for more or less T-

cells or B-cells B-Cells (bone marrow derived)

◦ 10-15% of all lymphocytes◦ Differentiate into plasma cells which secrete

antibodies which react to the antigens (pathogen or part of a pathogen)

Three types of lymphocytes

NK Cells (Natural Killer cells)◦ 5 – 10% of all lymphocytes◦ Attack normal cells infected with viruses or

foreign cells.

◦ Lymphocytes travel throughout your system. Most of them live for 4 years. Some can live for 20 years or more!

Hemoctyoblasts ◦ Produce lymphoid stem cells◦ Some remain in the bone marrow to make b-cells

and NK cells Lymphoid Organs

◦ Lymph Nodes Filter and purify lymph Located in regions where they can detect and

eliminate harmful intruders before they reach vital organs.

Thymus◦ T-cell maturation occurs here (located behind the

sternum)◦ 2 parts

Cortex – where T-cells divide and mature Medulla – where mature T-cells go in preparation to

enter the blood stream.

Spleen◦ In between stomach and left kidney◦ Blood flows through the spleen macrophages,

identify and engulf any damaged or infected cells.◦ Any abnormal antigens (pathogens) will produce

an immune response.

Lymph doesn’t affect cancer so that is typically the system that cancer uses to spread throughout the body (through the lymph glands)

Your body has two types of defenses Nonspecific Specific Nonspecific Defenses:

◦ Present at birth◦ Physical barriers

Epithelium (skin) Hair Cilia Mucus Digestive Juices

Phagocytes ◦ Microphages are found in the blood, when an

injury occurs they enter infected areas and basically eat pathogens

◦ Macrophages are found all over the body and are derived from monocytes in the blood. They are sensitive to chemicals released by foreign bodies. They work throughout your body eating pathogens before they can do harm to you.

Immunological Surveillance◦ NK cells identify cancer cells and cells that are

infected with a virus Complement

◦ Complement activation is when a protein in your body binds to the pathogen. This causes: Attraction to phagocytes Enhances phagocytosis Destroys cell membranes Promotes Inflammation

Inflammation◦ Results in swelling, redness, heat and pain◦ Mast cells release chemicals that cause:

Blood flow increase Phagocytes are activated Capillary permeability increases Complement is activated Clotting reaction walls off region Regional temperature is increased Specific defenses are activated.

Fever◦ Caused when the hypothalamus is influenced by

the presence of pyrogens released by toxins or antibody-antigen complexes

◦ Higher temperature speed up immune system. (104 or higher can be dangerous to you with CNS problems)

Provides immunity Specific to each pathogen Requires T-cells and B-cells 3 forms of immunity:

◦ Innate Immunity – genetically determined People not subject to diseases same as goldfish or

dogs◦ Active Immunity – When antigens are present they

stimulate the production of antibodies. These antibodies are specific to diseases. We also produce antibodies through controlled vaccinations. This is when we get sick

Specific Defenses: The Immune Response

Passive Immunity – when we acquire immunity through someone or something else. This would either be mother to child (through the placenta) or by taking antibodies to fight infection or diseases.

Specificity – each disease has its own antigen recognition.

Versatility – The immune system has to be ready for any infection. It can produce an appropriate and specific response to each antigen.

Memory – Our immune system remembers specific antigens. Therefore, if our body recognizes the same antigen again it can produce a faster and stronger attack.

Tolerance – Our immune system has a tolerance for our antigens. It doesn’t allow normal tissue to be attacked.

Properties of Immunity

T-Cells are activated by the presence of an antigen. This can occur by antigen-lymphocyte interaction. However, typically a receptor called the Major Histocompatibility Complex (MHC) is responsible.

How does MHC work?◦ Macrophages eat the pathogens, break them down

and send out recognition antigens. When a cells MHC comes in contact with the macrophage they then can display the antigen on their cell surface which will initiate an immune response.

T-Cells and Cellular Immunity:

Coordinate specific and non-specific defenses.

Stimulate cell mediated immunity and antibody-mediated immunity.

These are the cells affected in the disease of AIDS. The body doesn’t produce an immune response because these cells aren’t working.

Helper T-Cells

Helper T-Cells bind to inactive B-cells and cytotoxins.

Stimulates B-cell activation. Stimulates B-cell division (some go on to plasma

cells and some remain as memory B-cells) Accelerates Plasma cell production Antibodies are created. Memory B-cells act the same as Memory T-cells.

If the same pathogen is in the body they recognize it and immediately turn to plasma cells which create antibodies.

B-cells and Antibody-Mediated Response

Antibodies are also called immunoglobulins IgG – Responsible for defense against many

viruses, bacteria and bacterial toxins IgM – Responsible for reactions to

incompatible blood types. IgA – Attack pathogens before they enter

the body tissues. IgE – Accelerates inflammation based on

exposure to antigens IgD – Binds antigens to B-Cells

5 Different classes of Antibodies

Neutralization – Antibodies bind to toxins or viruses making them inactive.

Agglutination and Precipitation – Several antibodies bind to the same pathogen and form a clump (cell agglutinate or come together) and then precipitate out of the blood system.

Activation of Compliment – The antibody binds to the antigen and it changes the shape, which destroys the pathogen.

Antibodies can function in 6 ways

Attraction of Phagocytes – Binding causes phagocytes to recognize the intruder.

Enhancement of Phagocytes – binding makes the phagocytes more effective.

Stimulation of Inflammation – slows the spread of infection.

Autoimmune Disorders – The body attacks itself.

Immunodeficiency disorders – The immune system fails to develop or is blocked in some way.

Allergies – caused by antigens called allergens.

Types of Immune Disorders