The Immune System

Disease Transmission

o Robert Koch- “father of disease”o research focused on anthraxo Koch’s Postulates

NonSpecific Defenses

Initial reaction of body to ALL pathogens Pathogen-any agent that causes disease▪ Ex: bacteria, virus, fungi, parasites

Come into contact with the body by: Air Food Water Person-to-person contact Animal bites

NonSpecific Defenses:First Line of Defense

Skin – prevents entry Oil – traps and kills invaders Sweat-have toxins that can kill bacteria Mucous Membranes – epithelial tissue that protect the interior

surfaces of the body.▪ Mucous-sticky fluid that traps pathogens

Hair/Cilia▪ Respiratory tract into digestive tract

Tears Saliva Ear wax

NonSpecific Defenses:Second Line of Defense

If a pathogen penetrates the first line of defense... Inflammatory Response: series of reactions that suppress infection and speed

up recovery.1. Cells are damaged. Ex: cut, pathogen invasion2. Damaged cells release histamineo Causes increased blood flow and permeability of blood vessels around

injured areao Histamine causes redness, swelling, warmth, paino Sends signal to white blood cells to come

3. White blood cells (Phagocytes) arriveo Phagocytes ingest and destroy pathogens o 2 Types of Phagocytes: Neutrophils & Macrophages

4. Platelets arrive-seal off surrounding tissues and stop pathogens from entering the rest of the body

Inflammatory Response

Phagocyte

Neutrophil chasing bacteria

NonSpecific Defenses:Second Line of Defense

Natural Killer Cells-large white blood cells that attack pathogen-infected cells Can kill cancer cells and virus-infected cells Pierces cell membrane to kill the cell

Fever Increase in body temperature Slows growth of bacteria and viruses Promotes WBC activity

Complement System Proteins circulate in blood and become active when they encounter certain

pathogens Some puncture infected cell membranes to kill the cell

Interferon Protein released by virus-infected cells Causes nearby cells to make proteins that help them resist the virus infection

Natural Killer Cells

Specific DefensesThe Immune System

When pathogens get past the NonSpecific Defense…Aimed at SPECIFIC pathogens

o Immune System-cells and tissues that recognize and attack foreign substanceso Tissues:

o Bone marrow-makes lymphocyteso Thymus-gland where T cells matureo Lymph nodes-contain lymphocytes, filter lympho Spleen-stores healthy blood cells, breaks down old blood cells, helps develop

lymphocytes and other WBC, collects pathogens o Tonsils & Adenoids- masses of lymph tissue found in nose and throat that

contain lymphocytes which produce antibodieso Cells:

o Lymphocytes (WBC of the immune system)o 2 Types:o B Cells-made in bone marrow and mature thereo T Cells-made in bone marrow, but mature in thymus

Immune System Diagram

Lymphocytes

Recognizing Pathogens

Lymphocytes react to presence of antigens Antigens-proteins on the surface of pathogens

Lymphocytes have unique receptors on surface that match specific antigens

Matching lymphocytes bind to antigen to start attack

Immune Response-reaction of the body against pathogens

Immune Response

An immune response begins with: 1) Macrophage engulfs a pathogen 2) Macrophage displays fragments of the

pathogen’s antigens on its surface 3) Helper T cell (lymphocyte) with matching

receptors to the antigens binds to the macrophage 4) Macrophage releases proteins that activate

more helper T cells

Immune Response-Part 1

The immune response occurs in 2 parts, which happen simultaneously

Part 1- Cell-Mediated Immune Response Increase in Helper T cells and their division rates Cytotoxic T cells are produced▪ Recognize and destroy pathogen-infected cells▪ Cytotoxic T cells have receptors that match antigens▪ Puncture the cell membrane to kill it

Cell-Mediated Immune Reponse

Immune Response-Part 2

Part 2- Humoral Immune Response B cells that have matching receptors to the antigen

divide Change into plasma cells and memory cells▪ Plasma cells-make antibodies

Antibodies-defensive proteins that are released into blood

▪ Antibodies bind to specific antigen ▪ They do not destroy the pathogens directly

Humoral Immune Response

Primary and Secondary Immune Responses

o Some B cells turn into memory cellso Lymphocytes that will not respond the 1st time they meet an

antigen, but will recognize and attack with later infectionso Explains why you get most diseases only once

o Primary Immune Responseo First time the body encounters an antigeno Memory cells produced for that specific antigen

o Secondary Immune Responseo Later infection by the same pathogeno Memory cells respond faster and stronger

o Exception: Cold and Flu viruses

Immunity and Vaccinations

Immunity-the ability to resist an infectious disease Memory cells Vaccinations

Vaccine-solution that contains a dead or weakened pathogen Body produces primary immune response▪ Memory cells

Booster shots

Vaccination

Immune System Problems

Can react to harmless antigens in ways that can be harmful Allergies, Asthma, Autoimmune

Diseases

Allergy-a physical response to an antigen Many symptoms due to histamine▪ Antihistamines-drugs that counteract

effects of histamines and relieve symptoms of allergies

Immune System Problems

Allergies can trigger Asthma Respiratory disorder ▪ Bronchioles narrow▪ Swelling and inflammation ▪ Difficulty breathing

Autoimmune Diseases Disease where the immune system attacks the organism’s own

cells Ex: Multiple sclerosis

▪ Nervous system▪ T cells attack insulating material in nerve cells in the brain, spinal cord,

and nerves in eye▪ Cause weakness, tingling, blurred vision

Severe cases can cause paralysis, blindness, death

HIV and AIDS AIDS- Acquired Immunodeficiency Syndrome

The immune system loses its ability to fight off pathogens and cancers AIDS results from infection by HIV

HIV-Human Immunodeficiency Virus▪ Destroys Helper T cellscripples the immune systemleads to AIDS

Opportunistic Infections-illnesses caused by pathogens that produce disease in people with weakened immune systems Usually these pathogens don’t create problems in healthy people

HIV does NOT cause death, but AIDS is fatal Death caused by weakened immune system’s inability to fight

opportunistic infections and cancers HIV is transmitted by body fluids and contaminated needles

*PLAY DISCOVERYEDUCATION VIDEO*

Summary of Cell Types

Type of Cell Function

Macrophage Engulfs and kills pathogensHelps initiate immune response

Neutrophil Engulfs and kills pathogens

Natural Killer Cell Punctures infected cells

Helper T Cell Activates cytotoxic T cells Helps B cells multiply to form antibodies

Cytotoxic T Cell Puncture labeled infected cells

B Cell Labels invaders for destruction by macrophage

Plasma Cell Releases antibodies

Memory Cell Stores information about a pathogen