Immunity What is Immunity?

Immunity Immune System Immune Responses 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 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 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 bacteria

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 Fever Interferon Caused by the release of Histamine from leukocytes (WBC)   Fever The body releases more white blood cells The body then releases chemicals, histamines, that stimulate the action of these white blood cells by increasing the body’s temperature The high temp kills invaders by denaturing their proteins 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 Response Pathogens Pathogens eaten by Macrophage Displays portion of Pathogen on surface Helper-T cell recognizes Pathogen Step 1 Step 2 Step 3

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

Types of immunity Cellular Immunity Antibody Immunity Carried out by T-Cells Infected cells are killed by Cytotoxic T –Cells. 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. Macrophage ingests antigen and displays portion on its surface. Helper T- Cell recognizes antigen on the surface of the macrophage and becomes active. Active Helper T-Cell activates Cytotoxic T-Cells and B-Cells. 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. Supressor T-Cells stop the immune response when all antigens have been destroyed.

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 2nd 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 This is immunity where the body is “actively” producing antibodies to fight infection. Ex: You have a throat infection and you are actively creating antibodies to fight it. 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 is immunity where antibodies are given to a person from the blood of another person or animal. This immunity only lasts for a short period of time. ex: Breastfeeding mothers pass antibodies to their children through the milk.

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: No known cures. Usually treated with drugs.

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