IMMUNITY WHAT IS IMMUNITY Immunity The ability of

IMMUNITY WHAT IS IMMUNITY?

• Immunity • The ability of the body to fight infection and/or foreign invaders by producing antibodies or killing infected cells. • Immune System • The system in the body responsible for maintaining homeostasis by recognizing harmful from non-harmful organisms and produces an appropriate response. • The immune system is our primary defense against disease-causing microorganisms (foreign invaders). • Immune Responses 1. 2. Nonspecific defenses Specific defenses

NON-SPECIFIC DEFENSES • Not directed against a particular pathogen • Guards against all infections

1. THE SKIN & OTHER BARRIERS – FIRST LINE OF DEFENSE • Skin • • Most important nonspecific defense Provides Physical and Chemical barriers • Physical – hard to penetrate, made of indigestible keratin (layers of older dead skin cells) • Chemical – tears, sweat and oil glands produce an acidic environment where no pathogens can survive

• Other barriers • Mucus – lines the nasal cavity and throat that trap viruses and bacteria • Cilia – in trachea trap bacteria and sweep them up toward mouth – swallowed • Stomach acid and enzymes – destroys pathogens who make their way down the digestive tract • Lysozyme – an enzyme found in many body secretions, breaks down the cell walls of many

2. INFLAMMATORY RESPONSE – SECOND LINE OF DEFENSE • Phagocytes • White blood cells that engulf and destroy bacteria • Macrophages are a type of WBC that can carry out phagocytosis • leads to the macrophages becoming an antigen-presenting cell where the antigens are ingested by macrophages and displays a portion of the antigen on it’s surface • makes it easier for the cells of the immune system to recognize and initiate the immune response

• Inflammation • Caused by the release of Histamine from leukocytes (WBC) • • Fever • • The body releases more white blood cells • The high temp kills invaders by denaturing their proteins The body then releases chemicals, histamines, that stimulate the action of these white blood cells by increasing the body’s temperature • Interferon • A protein produced by infected cells to help other cells resists viral infection • It interferes with the synthesis of viral proteins and helps block viral replication

SPECIFIC DEFENSES • This is a specific response to a specific pathogen/antigen • Antigens are carbohydrates, proteins, and lipids on the surface of viruses, bacteria and other pathogens that trigger a specific immune response • The response involves the creation of Antibodies • • Antibodies • Y-shaped protein molecule. • Produced by B-Lymphocytes (a type of WBC) • Function: Recognize antigens, bind to and deactivate them. • Note: Variable region recognizes the anitgens.

• The immune system is made up of a network of cells, tissues, and organs that work together to protect the body. • The cells involved are white blood cells, or leukocytes, which come in two basic types that combine to seek out and destroy disease-causing organisms or substances.

THE TWO BASIC TYPES OF LEUKOCYTES ARE: 1. phagocytes • cells that chew up invading organisms • a number of different cells are considered phagocytes • most common type is the neutrophil, which primarily fights bacteria

2. lymphocytes • cells that allow the body to remember and recognize previous invaders and help the body destroy them • • The two kinds of lymphocytes are B lymphocytes and T lymphocytes. B lymphocytes • • • start out in the bone marrow and stay there and mature into B cells B lymphocytes are like the body's military intelligence system, seeking out their targets and sending defenses to lock onto them T lymphocytes • start out in the bone marrow and they leave for the thymus gland, where they mature into T cells • T cells are like the soldiers, destroying the invaders that the intelligence system has identified

DEACTIVATION OF A BACTERIUM BY AN ANTIBODY.

THE PATHWAY OF SPECIFIC IMMUNE Step 1 RESPONSE Pathogens eaten by Macrophage Step 2 Displays portion of Pathogen on surface Step 3 Pathogens Helper-T cell recognizes Pathogen

Activates B- Cell Activates Cytotoxic T- Cell Memory T-Cell Kills Infected Cells Memory B-Cell Antibodies

TYPES OF IMMUNITY CELLULAR IMMUNITY • Carried out by T-Cells • Infected cells are killed by Cytotoxic T –Cells. ANTIBODY IMMUNITY • Carried out by B-cells • Antibodies are produced and dumped into blood stream. • Antibodies bind to antigens and deactivate them.

IMMUNE RESPONSE EXPLAINED • • • Antigen infects cells. • • • Active Helper T-Cell activates Cytotoxic T-Cells and B-Cells. • Supressor T-Cells stop the immune response when all antigens have been destroyed. Macrophage ingests antigen and displays portion on its surface. Helper T- Cell recognizes antigen on the surface of the macrophage and becomes active. Cytotoxic T-Cells divide into Active Cytotoxic T-cells and Memory T – Cells. Active Cytotoxic T-Cells kill infected cells. At the same time, B-Cells divide into Plasma Cells and Memory B- Cells. Plasma cells produce antibodies that deactivate pathogen. Memory T and Memory B cells remain in the body to speed up the response if the same antigen reappears.

PRIMARY. VS. SECONDARY IMMUNE RESPONSE • Primary Immune Response • This is a response to an invader the First time the invader infects the body. • • No measurable immune response for first few days. Next 10 – 15 days antibody production grows steadily • • Secondary Immune Response • A more rapid response to an invader the 2 nd time it invades the body. • Antibody production increases dramatically and in a much shorter time period.

PRIMARY. VS. SECONDARY IMMUNE RESPONSE

PASSIVE. VS. ACTIVE IMMUNITY • • Active Immunity • Ex: You have a throat infection and you are actively creating antibodies to fight it. This is immunity where the body is “actively” producing antibodies to fight infection. • Vaccination: An injection of a weakened or deadened strain of an infectious microbe (pathogen) that causes the body to undergo active immunity (produce antibodies). • • Passive Immunity • This immunity only lasts for a short period of time. • ex: Breastfeeding mothers pass antibodies to their children through the milk. This is immunity where antibodies are given to a person from the blood of another person or animal.

AUTOIMMUNE DISEASE • Autoimmune diseases are diseases where the immune system begins to attack itself. • Ex: • Rheumatoid Arthritis – crippling disease of the joints. • Lupus – disease of blood and organs. • Multiple Sclerosis – disease of nervous system • Cause(s): unknown • • Cures/Treatments: with drugs. No known cures. Usually treated

ALLERGIES • Allergy • - An exaggerated response by the immune system to an allergen. • Allergen: a normally harmless substance that causes an allergic reaction. • ex: dust, pollen, mould, food, insect stings • • Types of Allergic reactions • There are two types of allergic reactions. • 1. Immediate – occurs within seconds and normally lasts for about 30 mins. • 2. Delayed – takes longer to react and can last for a much longer time.

WHAT HAPPENS DURING AN ALLERGIC REACTION? • During an allergic reaction antibodies cause histamines to be released from certain cells. • Histamines cause: • a. Swelling of tissues • b. Release of fluids (runny noses and eyes) • c. muscle spasms (some cases)

• Anaphylaxis or anaphylactic shock: • This is the sudden and severe allergic reaction to a substance that can cause death. • • Treatments for Allergies • Avoidance of material – especially food. • Epinephrine – “epi – pen” • Antihistamines -- benadryl