The Immune System

Primary functions of the Lymphatic System

¡  Return of fluid from body tissues to the blood.

¡  The distribution of hormones, nutrients, and waste products from their tissues of origin to the general circulation.

¡  The defense of the body from infection and disease.

Body’s lines of defense ¡  1st line of defense:

- Skin and mucous membranes - Nonspecific immunity:

protects against antigens. - Body secretions aid in control

of pathogenic organisms. ¡  2nd Line of defense:

Inflammatory response - Nonspecific immunity: special

cells that patrol the body and destroy invading antigens.

¡  3rd Line of defense: Immune response

- Specific immunity : special cells that target specific antigens, known as antibodies and complements.

•  All lines of defense work together, if one is successful the others shut off.

•  An antigen is a foreign material in the environment capable of causing an immune response in the body.

Origin of cells ¡  Blood cells originate

in the bone marrow.

¡  Develop from stem cells

¡  Types of cells: - RBC’s: develop from

erythroid stem cells and mature in bone marrow.

¡  WBC’s: develop from myeloid stem cells. Mature into eosinophils,

neutrophils & basophils. ¡  Lymphocytes: develop

from lymphoid stem cells.

Components of the Lymphatic System

¡  Made up of a network of lymphatic vessels, lymph and lymphoid organs.

¡  Lymph is the fluid that flows through the lymphatic vessels.

¡  Lymphocytes and other protective cells within the lymphatic organs filter foreign matter and pathogens from the lymph.

Lymph Nodes ¡  Function: act as a

filter, it filters and purifies the lymph before it reaches the venous system.

¡  Located in regions where they can guard or trap harmful “intruders” before they reach vital organs of the body.

¡  When infection is present in the body the lymph nodes become inflamed or swollen, due to increased activity.

Thymus ¡  Located in the

mediastinum posterior to the sternum.

¡  Main function: produce and store T cells.

¡  T cell lymphocytes become mature within the thymus.

¡  The T cells divide in the cortex and migrate to the medulla, then are distributed throughout the body.

¡  Produces the thymic hormones (thymosins).

Spleen

¡  Contains the largest collection of lymphoid tissue.

¡  Located between the stomach, the left kidney and the diaphragm.

¡  Deep red in color due to the amount of blood it contains.

¡  Functions: ¡  Removes abnormal

blood cells and components.

¡  Stores iron from recycled red blood cells.

¡  Monitors and responds to pathogens and foreign antigens in the circulation blood.

Cell Markers ¡  Allow cells to recognize and communicate

with each other. ¡  Allows cells to recognize “self” or non-self”. ¡  All body cells carry molecules that are

encoded by a group of genes known as MHC (major histocompatibility complex). Works like a finger print on cell so they can identify “self”.

¡  When immune cells meet foreign markers, they move quickly to destroy them.

¡  Immune cells have the ability to remember previous encounters and react accordingly.

Lymphocytes ¡  Types of

lymphocytes: ¡  T cells ¡  B cells ¡  NK cells

¡  They are WBC’s, that are specialized to protect the body from antigens and pathogens.

T Cells ¡  Mature in the thymus. ¡  Act directly with their

targets. ¡  Do not make

antibodies. ¡  Major functions: - Aid in the operation of

other cells. - Helper T cells

(detective cells) aid in the activation of the B cells and other T cells.

- Activate Natural Killer cells (NK) and macrophages.

- Suppressor T cells turn off these cells.

- Killer T cells act directly on infected or malignant cells, or other target antigens.

- Attach to target, secrete chemicals, which make holes in targets membrane and then destroy it.

- Causes rejection of tissues and organ transplants.

B Cells

¡  Responsible for the production and secretion of antibodies, known as immunoglobulins.

Immunoglobullins

¡  Known as the “foot soldiers” ¡  IgG: coats organisms to speed the

uptake by other immune system cells. ¡  IgM: kills bacteria. ¡  IgA: guards the entrances of the body. ¡  IgE: plays important role in allergies. ¡  IgD: regulates the B cell’s activities

NK Cells ¡  Have the ability to recognize abnormal cells ¡  Attack the following: ¡  Foreign cells ¡  Normal cells infected with viruses. ¡  Cancer cells that appear in normal tissues. ¡  Continually monitor the body tissues, this is known as immunological surveillance. ¡  AIDS virus inactivates NK cells.

Immune Response ¡  Goal is to destroy of inactivate pathogens,

abnormal cells or toxins.

What can affect the body’s immune response?

¡  Nutrition ¡  Mental and

emotional health ¡  Exercise ¡  Levels of zinc,

iodine, fats, sugar and fiber.

¡  Personality ¡  Environment

Complement system & Inflammation ¡  Complement is a group

of 25 inactive enzyme proteins present in the blood.

¡  When one complement protein meet an antibody-antigen complex, it activates a chain reaction.

¡  It attracts other cells and molecules to aid the antibodies in destroying the bacteria.

¡  Inflammation: ¡  If a tissue is injured,

complement proteins begin to act.

¡  Basophils and Mast cells are activated and release histamine.

¡  Histamine dilates blood vessels, slowing down the rate of blood flow. The vessel walls become permeable, which allows fluid to seep into the surrounding tissues.

¡  The result is localized warmth, redness and swelling.

Types of Immunity ¡  Active immunity:

develops when a person makes their own immunity.

¡  By having the disease. (e.g., chicken pox, measles)

¡  By receiving the vaccine of a live or weakened organism.

¡  Long lasting immunity.

¡  Passive immunity: antibodies developed in another individual’s immune system are injected into a non-immune individual (e.g., tetanus)

¡  This immunity does not last long.

¡  Vaccines cause the production of antigen-antibody complex followed by memory cells.

Inflammatory Response

Diseases and disorders of the immune system:

¡  AIDS: Caused by the HIV virus. ¡  Fragile outside the body. ¡  Destroys the immune system. ¡  Found in body fluids: blood, semen, vaginal

secretions ¡  Virus hides in the body for months or even

years. ¡  Opportunistic infections that normally would

not cause disease in a person with a strong immune system, are often resistant to tx.

¡  Diagnosed by a positive ELISA ¡  Western Blot and IFA are used to confirm a

positive ELISA.

Allergies

¡  Hypersensitivity to harmless environmental antigens.

¡  When exposed to allergens, IgE is produced resulting in allergic symptoms.

Cancer ¡  Uncontrolled growth and

spread of abnormal cells. ¡  Warning Signs: - Change in bowel or bladder

habits. - Sore that does not heal. - Unusual bleeding or

discharge. - Thickening or lump. - Indigestion or difficulty in

swallowing. - Obvious change in wart or

mole. - Nagging cough or

hoarseness.

¡  Benign: tumors in which cells divide but stay in one place forming a mass.

¡  Malignant: Tumor cells that spread into surrounding tissue and organs.

¡  Metastasis: change in membrane proteins that cause cells no to bind to each other as a tissue.

Spread occurs to other parts of body through the blood.

¡  The body develops cancer cells continuously but. The immune system destroys them.

Chronic Fatigue Syndrome ¡  Debilitating disorder, maybe genetically

related. ¡  Sx: persistent fatigue, low grade fever, sore

throat, swollen lymph nodes, headaches, unexplained muscle weakness or pain, joint pain, forgetfulness, confusion, irritability, depression and sleep disturbances.

¡  Treatment: Analgesics for pain, antihistamines for allergic symptoms, antidepressants to improve sleep and fatigue.

Rheumatoid Arthritis

¡  Chronic systemic inflammatory autoimmune disease.

¡  Affects joints and surrounding muscles, tendons, ligaments, and blood vessels.

¡  Women affected 3 times more often than men.

Lupus ¡  Chronic disease of unknown cause. ¡  Affects women 9 times more than men. ¡  Causes: inflammation of various parts of

the body including skin, joints, kidneys, lungs, heart, nervous system, and other organs and system.

¡  Antibodies react against the person’s own tissue.

¡  Three types: Cutaneous, systemic or drug induced.

Questions ?

l Where do B cells mature? l What is a cell marker? l What is meant by recognizing “self” and

“nonself”? l What is the role of the B cell in the

immune system? l What is the role of the T cell in the

immune system? l Explain the cause of the inflammatory

response. l What are the body’s three lines of

defense?