The Immune System Activate your Prior Knowledge Discuss

The Immune System

Activate your Prior Knowledge! • Discuss with a partner: • What do you remember about the immune system? What is it? • How does it protect your body? • Why does your body get sick? • How come when you get injured, that area tends to become red and feel warm?

If microbes are everywhere, why aren’t we sick all the time? • Microorganisms are EVERYWHERE!!! • Bacteria thrives on your skin E. g. Staphylococcus and Streptococcus species • Bacteria colonizes your large intestines E. g. E. coli How many grams of bacteria inhabit our bodies? - 1 gram, 1000 g?

Answer 1000 grams or 1 kilogram!!! There are more bacteria in and on our body than human cells

What is the immune system? • The body’s defense against disease causing organisms, malfunctioning cells, and foreign particles • It is made up of networks of cells, tissues, and organs

First Line of Defense • Innate or non-specific defense responses. Including: o o o Skin Tears Saliva Cilia and mucous Gastric juice in your stomach

Skin

Skin • The outer most layer of skin is made up of 20 -30 layers of dead epithelial (skin) cells. • Serves as a protective barrier against microbes (bacteria and viruses) and other foreign substances.

Tears • Aka lacrimal secretion • Continuously lubricates and cleanse eyes • Contains lysozyme – an enzyme that destroys bacteria

Saliva • What’s the first thing you do when you cut your finger? • Saliva contains many chemicals that break down bacteria • However, thousands of different types of bacteria can survive these chemicals • Also contains lysozyme

Cilia and Mucus

Cilia and Mucus • Cilia o Propel debris-laden mucus away from nasal cavity and lower respiratory passages o Directs them out of the body • Mucus o Traps microorganisms and foreign particles from respiratory and digestive tracts.

Stomach Acid • Swallowed bacteria are broken down by incredibly strong acids in the stomach • What is this acid? o Hydrochloric Acid (HCl) o p. H below 2 • How does the stomach protect itself from the acid?

Stomach Acid

Review • First Line of Defense o o o Skin Tears Saliva Cilia and mucous Gastric juice in your stomach • Acts as a barrier that prevents pathogens from entering the body. • As long as pathogens stay outside the body this defensive line will handle things just fine.

Exit Slip • What is found in both tear and saliva that can destroy harmful bacteria? • How does the 1 st line of defense defend your body from infections and diseases?

Second Line of Defense • AKA innate or non-specific defense (immune) responses. • Includes: o o White Blood Cells (macrophages and neutrophils) Inflammation Fever Interferon

White Blood Cells • Macrophages o “Big eaters” o Phagocytic – engulfs foreign particles • Neutrophils o Most abundant white blood cell o Phagocytic – engulfs foreign particles • Once engulfed, the phagocyte breaks the foreign particles apart in organelles called Lysosome.

• Note the difference between Lysosome and Lysozyme, they both break down foreign particles but Lysosome is an organelle and Lysozyme is an enzyme.

Inflammatory Response • Is triggered whenever body tissues are injured. E. g. cuts, scrapes, bone fractures, infection, etc. • Injured body cells release chemicals called histamines, which begin inflammatory response • Histamines are produced from basophils AND mast cells.

Inflammation • 4 classical symptoms: o Redness o Swelling o Heat o Pain

Main events in Inflammation 1) Vasodilation – capillaries dilate to allow blood to flow to injured area o This is responsible for the redness and heat. o Allows WBCs flock to infected area like sharks to blood 2) Dilated capillaries increase permeability, so fluid and cells are able to leak out, this causes swelling.

Fever • Systemic response to invading microorganisms • Abnormally high body temperatures above 37 o. C • Pyrogens are chemicals released from macrophages, reach hypothalamus, and temperature rises • (Pyro = Fire)

Viruses • Viruses enter body cells, hijack their organelles, and turn the cell into a virus making-factory. The cell will eventually burst, releasing thousands of viruses to infect new cells. Cell before infection… …and after.

Interferon - Virus-infected body cells release interferon when an invasion occurs - Interferon – chemical that interferes with the ability of viruses to attack other body cells • What happens to already Infected cells?

Antigens • Are substances that initiates the third line of defense and causes your immune system to produce antibodies • Could be any foreign substance from the environment o E. g. Chemicals, bacteria, viruses, pollen

Antigen

Third Line of Defense • Adaptive or specific defense system • Includes: o Humoral Immunity • B lymphocytes production of antibodies o Cell-Mediated Immunity • T lymphocytes • Both B and T lymphocytes are produced in the bone marrow

Bone Marrow

Third Line of Defense • 3 important aspects: 1) It is specific 2) It is systemic 3) It has “memory” Takes longer to activate than non-specific responses.

Humoral Immunity • Also known as the antibody mediated immunity • B lymphocytes mature in the bone marrow o Are antibody producing cells • These are called plasma cells o Antibodies are Y-shaped molecules

Antibody • Antibodies have receptors to bind to antigens

Cell-Mediated Immunity • Involves living cells as protective factors • These cells are T lymphocytes o Recognizes infected human cells and cancer cells o T lymphocytes will attack these infected cells, quickly kill them, and then continue to search for more cells to kill o T lymphocytes mature in the thymus gland

Thymus Gland

T Lymphocytes • Different types of T cells • Th – T helper cells o Activates all aspects of immune response • Tc – cytotoxic T cells (killer T cells) o Highly specific, kill abnormal cells

Helper T Cells • Primary task is to activate B cells and cytotoxic T cells. • BUT they themselves must be activated

Activation of Helper T Cells

Activation of Cytotoxic T Cells • All nucleated cells present antigens that represent what's happening in the cell • If something is not right (presents non-self antigen), then the Cytotoxic T cells will detect this and kill the cell • Secrete specialized proteins called perforins that poke holes in cell membrane and granzymes that tell the cell to kill itself. • Note* require activation factors from an activated T helper cell to become active

Activation of B cells and production of plasma and memory cells.

Humoral rev isited • used to fight all threats • Does so by the production of antibodies (AKA immunoglobulins) • Antibodies serve several functions: - Attract phagocytes - Complement system activation (pokes holes in bacterial causing them to lyse) - To neutralize certain toxins (example snake venom)

Cell mediated revisited • used to fight intracellular pathogens or abnormal cells • Does so by killing infected (virus, bacteria, parasite) cells or abnormal cells.

Immunological Memory • Primary Immune Response: o First time the body encounters a particular antigen o Antibodies detected in serum between 7 -10 days

Immunological Memory • Secondary Immune Response: o Upon re-exposure to the same antigen, the body’s immune response will be much faster, more effective and prolonged since memory cells have been made previously that target for these types of antigens specifically. o Antibodies detected in the serum between 3 -5 days.

Antibody response after exposure to antigen

What is immunity? • Resistance to disease causing organism or harmful substance • Two types - Active Immunity - Passive Immunity

Active Immunity - YOU produce the immune response! (e. g. antibodies) - Your body has been exposed to the antigen in the past either through: - Natural exposure (daily exposure to foreign particles) - Artificial exposure (immunizations/vaccines) - You fought it, you won, you remember it - Active immunity develops slowly but lasts for years.

Passive Immunity • • You DON’T produce the immune response directly Pre-made antibody molecules enter the body Immediate effect Short duration (2 weeks to 1 month) o Natural (A mother will pass immunities on to her baby during pregnancy) • Through what organ? Placenta o Artificial (antibody produced in another host injected. E. g. anti venom)

Active Immunity Passive Immunity

How long does active immunity last? • It depends on the antigen • Some disease-causing bacteria and viruses mutate into new forms that our body doesn’t recognize, requiring annual vaccinations, like the flu shot • Booster shot - reminds the immune system of the antigen

It’s time to get an STI • Exchange body fluids with 4 other people (mix both solutions together and then divide equally between the two beakers)

Vaccines are the victims of their own success • https: //www. youtube. com/watch? v=gpl. A 6 pq 9 c. Os

R 0 • Known as a the basic reproduction number • Expected number of cases directly generated by one case in a population (ie. How many people will one person infect) If R 0 > 1 then the number of cases is growing If R 0 < 1 then the number of cases is declining

Herd Immunity • the resistance to the spread of a contagious disease within a population that results if a sufficiently high proportion of individuals are immune to the disease, especially through vaccination. • Measles, the most contagious virus on earth, needs to have as much as 95% of a population immunized in order to have a R 0 < 1

Think the flu is no big deal? • Think again… • In 1918, a particularly deadly strain of flu, called the Spanish Influenza, spread across the globe • It infected ~one third of the human population and killed ~100 million people (5% of population)

HIV • HIV stands for Human Immunodeficiency Virus • It is found in blood, semen, and vaginal secretions. • The virus commonly enters the body through blood transfusions or blood-contaminated needles and during sexual intercourse.

HIV • HIV attacks the helper T cells of the immune system • Therefore, activation of B lymphocytes and cytotoxic T cells cannot occur. • HIV doesn’t kill you – it cripples your immune system

AIDS • AIDS stands for Acquired Immune Deficiency Syndrome • It is caused by HIV • Diseases your immune system can normally defeat now becomes lifethreatening • The first symptoms of AIDS are similar to those of a cold.

Self and Non-self • Our immune system has an incredible ability to recognize our cells as “self” and foreign cells as “non-self” • Our own cells carry distinctive “self” marker molecules that tell the immune system to leave those cells alone and to not destroy them.

Self and Non-self • Recall, foreign “non-self” cells that are capable of triggering an immune response.

Organ Transplants • Cells and tissues from another person carries their own self markers and therefore, will be recognized as “nonself” in our bodies. • This is the reason why some organ transplants are rejected and unsuccessful.

Organ Transplants There are 4 major types of transplants called grafts. 1. Autografts – tissue grafts transplanted from one body site to another from the same person. 2. Isografts – graft from a genetically identical individual. E. g. identical twin

Organ Transplants 3. Allografts – grafts from the same species but not from a genetically identical individual 4. Xenografts – grafts from animals

Immune Disorders

Autoimmune Diseases • Results when the body’s immune system fails to recognize its own body cells • It launches an attack against its own cells thinking that they are foreign antigens

Autoimmune Diseases • Examples of autoimmune diseases are rheumatoid arthritis and type 1 diabetes. • These diseases cannot be cured, they can only be treated to relieve symptoms and prevent long-term damage

Allergies - Immune system forms an improper immune response to harmless foreign particles - causes sneezing, runny nose, and watery eyes - Anti-histamines block effect of histamines and bring relief to allergy sufferers Name some things people might be allergic to?

Lymphatic System • The lymphatic system is a major part of the immune system • It is made up of o Lymphatic vessels o Lymph nodes o Lymph

Lymphatic Vessels • Lymphatic vessels consists of blind-ended tubes which carries lymph in one direction – only towards the heart. • Lymph is made up of the fluid leaked from blood • (lymph = clear water) • Pathogens and cancer cells may spread throughout the body via the lymphatic stream

Lymphoid Cells • Lymphoid cells include lymphocytes, plasma cells and macrophages.

Lymph Nodes • Significant lymphoid organ • Function: o Filter lymph – by using macrophages to remove and destroy microorganisms and other debris o To help activate the immune system – high density of immune cells

Other Lymphoid Organs Spleen • Largest lymphoid organ • Function: o Destroys old and defective red blood cells o High density of immune cells (lymph node of the “blood”)

Other Lymphoid Organs Thymus • Most active during early years of life. • Function: o Site of T lymphocyte maturation

Other Lymphoid Organs Tonsils • Simplest lymphoid organ • Function: o Gather and remove many of the pathogens entering the pharynx in food or in inhaled air.

Functions of lymphatic system revisted • Body fluid balance – takes up excess fluids in tissues • Immune – has sites of high immune cell density (nodes) which “sample” body for pathogens • Fat transport – transports absorbed fats from S. I. into blood circulation