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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. • Highly specific recognition of foreign antigens • Mechanisms for elimination of microbes bearing such antigens • A vast universe of distinct antigenic specifies • Immunologic memory • Tolerance of self-antigens
Key attributes of immune system • 4 attributes that characterize the immune system as a whole – specificity • antigen-antibody specificity – diversity • react to millions of antigens – memory • rapid 2° response – ability to distinguish self vs. non-self • maturation & training process to reduce auto- immune disease
Foreign Invaders • Called Pathogens – Viruses, bacteria or other living thing that causes disease/immune response. • Antigens – Toxins that pathogens produce that cause harm to an organism.
Avenues of attack• Points of entry – digestive system – respiratory system – urogenital tract – break in skin• Routes of attack – circulatory system – lymph system
Parts of the Immune System 1. Blood - White Blood Cells in particular. 2. Lymph nodes 3. Thymus Gland – Produces T Lymphocytes 4. Bone Marrow – Produces B Lymphocytes
Production & transport of leukocytesLymph system Traps foreign invaders lymph vessels (intertwined amongst blood vessels) lymph node
How does the body fight infection/foreign invaders? First Line of Defense – The Skin • Provides Physical and Chemical barriers • Physical – hard to penetrate, made of indigestible keratin • Chemical – tears, sweat
2nd Line – Nonspecific Immune Response These are defenses the body uses no matter what the invader may be. These defenses include: – Phagocytosis – done by Macrophages – Natural Cell Killers – Inflammation - caused by release of Histamine from leukocytes – Fever – caused by histamines. The fever (high temp) kills invaders by denaturing their proteins.
2nd line: Internal, broad range patrol • Innate, general defense leukocytes – rapid response • Patrolling cells & proteins – attack invaders that penetrate body’s outer barriers • leukocytes – phagocytic white blood cells • complement system – anti-microbial proteins • inflammatory response
Leukocytes: Phagocytic white blood cells (WBCs) • Attracted by chemical signals released by damaged cells – enter infected tissue, engulf & ingest microbes • lysosomes • Neutrophils – most abundant WBC (~70%) – ~ 3 day lifespan • Macrophages – “big eater”, long-lived • Natural Killer Cells – destroy virus-infected cells & cancer cells
Fever • When a local response is not enough – systemic response to infection – activated macrophages release interleukin-1 (IL-1) • triggers hypothalamus in brain to readjust body thermostat to raise body temperature – higher temperature helps defense • inhibits bacterial growth • stimulates phagocytosis • speeds up repair of tissues • causes liver & spleen to store iron, reducing blood iron levels – bacteria need large amounts of iron to grow
The Inflammatory Response• 1- Tissue injury; release of chemical signals~ • histamine (basophils/mast cells): causes Step 2... • prostaglandins: increases blood flow & vessel permeability• 2/3- Dilation and increased permeability of capillary~ • chemokines: secreted by blood vessel endothelial cells mediates phagocytotic migration of WBCs• 4- Phagocytosis of pathogens~ • fever & pyrogens: leukocyte-released molecules increase body temperature
3rd line: Acquired (active) Immunity • Specific defense – lymphocytes • B lymphocytes (B cells) • T lymphocytes (T cells) – antibodies • immunoglobulins • Responds to… – antigens • specific pathogens • specific toxins • abnormal body cells (cancer)
3rd Line – Specific Immune Response This is a specific response to a specific pathogen/antigen. The response involves the creation of Antibodies.
Antibodies • Y-shaped protein molecule. • Made up of variable and constant regions. • Made up of Heavy and Light chains. • Produced by B- Lymphocytes • Function: Recognize antigens, bind to and deactivate them. – Note: Variable region recognizes the anitgens.
Antigens- recognition of invaders • Antigens – proteins that serve as cellular name tags • foreign antigens cause response from WBCs – viruses, bacteria, protozoa, parasitic worms, fungi, toxins – non-pathogens: pollen & transplanted tissue • B cells & T cells respond to different antigens – B cells recognize intact antigens • pathogens in blood & lymph – T cells recognize antigen fragments • pathogens which have already infected cells “self” “foreign”
How an antibody operates/works? Deactivation of a bacterium by an antibody.
How are cells tagged with antigens?• Major histocompatibility (MHC) proteins – antigen glycoproteins – MHC I – on all nucleated cells – MHC II – on macrophages, B-Ly, activated T-Ly• MHC proteins constantly carry bits of cellular material from the cytosol to the cell surface – “snapshot” of what is going on inside cell – give the surface of cells a unique label or “fingerprint” T cell MHC proteins displaying self-antigens
The Pathway of Specific Immune Response Step 1 Pathogens eaten by Macrophage Step 2 Displays portion of Pathogen on surface Step 3Pathogens Helper-T cell recognizes Pathogen
Cellular Immunity vs. Antibody Immunity Cellular Immunity Antibody or Humoral Immunity • Carried out by T-Cells • Carried out by B-cells • Infected cells are killed by • Antibodies are produced Cytotoxic T –Cells. and dumped into blood stream. • Antibodies bind to antigens and deactivate them.
Immune Response Explained 1. Antigen infects cells. 2. Macrophage ingests antigen and displays portion on its surface. 3. Helper T- Cell recognizes antigen on the surface of the macrophage and becomes active. 4. Active Helper T-Cell activates Cytotoxic T-Cells and B-Cells. 5. Cytotoxic T-Cells divide into Active Cytotoxic T-cells and Memory T – Cells. 6. Active Cytotoxic T-Cells kill infected cells. 7. At the same time, B-Cells divide into Plasma Cells and Memory B- Cells. 8. Plasma cells produce antibodies that deactivate pathogen. 9. Memory T and Memory B cells remain in the body to speed up the response if the same antigen reappears. 10. Supressor T-Cells stop the immune response when all antigens have been destroyed.
Immune Response Summary Displays copy of antigen on surface of cell Antigen Macrophage Helper T - Cell Antibody Immunity Cellular Immunity Active Cytotoxic T-Cell Active B - CellKills Infected Cells Memory T- Cell Plasma Cell Memory B-Cell Antibodies Deactivates Antigens
Primary .vs. Secondary Immune Response • Primary Immune Response – This is a response to an invader the 1st 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..
Induction of Immune Responses• Primary immune response: lymphocyte proliferation and differentiation the 1st time the body is exposed to an antigen• Plasma cells: antibody-producing effector B-cells• Secondary immune response: immune response if the individual is exposed to the same antigen at some later time~ Immunological memory
Passive vs. Active Immunity 1. 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 strain of an infectious microbe (pathogen) that causes the body to undergo active immunity (produce antibodies). 1. 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.
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. a. Immediate – occurs within seconds and normally lasts for about 30 mins. b. 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 1. Avoidance of material – especially food. 2. Epinephrine – “epi – pen” 3. Antihistamines -- benadryl
HIV & AIDS • Human Immunodeficiency Virus – virus infects helper T cells – helper T cells don’t activate rest of immune system: T cells & B cells • also destroy T cells • Acquired ImmunoDeficiency Syndrome – infections by opportunistic diseases – death usually from other infections • pneumonia, cancer
HIV • HIV is a virus that specifically attacks the lymphocytes. • This means the number of lymphocytes decreases. • Less antibodies are made. • Predict the consequences…
Transmission of HIV • Infected blood – blood transfusions, sharing needles, • Infected semen and vaginal mucus – unprotected sex • Infected mother’s milk – low risk • Infected saliva – almost zero risk
AIDS• Caused by the HIV virus that selectively infects the immune system leaving the body open to infection by removing the specific immunity.
Social implications of AIDS • Cases of AIDS are not evenly distributed in the world, for example there are severe problems in Africa (some populations with 30% of their people are infected). • What cultural and economic reasons are there for differences in the prevalence of AIDS? • Is there a moral obligation of those with the technology and the wealth to help others lacking these things in the fight against AIDS?