Unit 8- THE IMMUNE SYSTEM

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 nonharmful organisms.

Foreign Invaders Called Pathogens Viruses, bacteria or parasite that causes disease/immune response. Toxins that pathogens produce may cause harm as well.

Parts of the Immune System Blood - White Blood Cells in particular Lymph nodes Thymus Gland – Produces T Cells Bone Marrow – Produces B Cells

The Body’s THREE lines of Defense First Line of Defense – The Skin Provides Physical and Chemical barriers Physical – hard to penetrate, made of indigestible keratin Chemical – tears, sweat

Second Line of Defense – Nonspecific Immune Response These are defenses the body uses no matter what the invader may be. These defenses include: Phagocytosis – done by macrophages Natural Killer Cells Inflammation - caused by release of histamine. Fever – caused by histamines. The fever (high temp) kills invaders.

Third Line of Defense This is a specific response to a specific pathogen. The response involves the creation of antibodies and killer cells.

White Blood Cells B-cells mature in bone marrow then concentrate in lymph nodes and spleen-Produce antibodies T-cells mature in thymus B and T cells mature then circulate in the blood and lymph Circulation ensures they come into contact with pathogens

B Cells Activated B cells produce lots of antibodies, about a 1000/sec. The antibodies travel to the blood, lymph, lining of gut and lungs. Antibodies stay in the blood longer but eventually their numbers go down.

B -Lymphocytes Some activated B cells become memory cells. Memory cells divide rapidly as soon as the pathogen is reintroduced. When the pathogen/infection infects again it is destroyed before any symptoms show.

T-Cells Two types: Helper T cells -help the immune response start Killer T cells -Kill body cells making new pathogen Memory T cells -remain in body

The Immune Response Explained Pathogens infect cells. Macrophage ingests pathogen and displays portion on its surface. Helper T- Cell recognizes pathogen on the surface of the macrophage and becomes active. Helper T-Cell activates Killer T-Cells and B-Cells.

The Immune Response Explained 5. Killer T-Cells kill infected cells. 6. At the same time, B-Cells start making antibodies which kill already made pathogens. 7. Memory T and Memory B cells remain in the body to speed up the response if the same antigen reappears.

Active and Passive Immunity Active immunity Lymphocytes are activated by antigens on the surface of pathogens Natural active immunity - acquired due to infection Artificial active immunity – vaccination Takes time for enough B and T cells to be produced to mount an effective response.

Active and Passive Immunity Natural passive immunity A mother’s antibodies pass across the placenta to the fetus and remain for several months. Colostrum (the first breast milk) contains lots of antibodies which help the baby fight infection

Vaccines A preparation containing anti-pathogen material: Whole live microorganism Dead microorganism

Vaccines Why aren’t they always effective? Natural infections persist within the body for a long time so the immune system has time to develop an effective response, vaccinations from dead pathogens do not do this. Less effective vaccines need booster injections to stimulate secondary responses

Allergies When the immune system responds to harmless substances Allergens – substances which do no real harm Allergens include house dust, animal skin, pollen, house dust mites and their feces

Autoimmune Diseases A. Autoimmune Diseases - Occur when the immune system no longer recognizes the cells of your own body… the immune system attacks healthy body cells. Examples include: Diabetes Mellitus Lupus Multiple Sclerosis (MS) Rheumatoid Arthritis Autoimmune diseases are more frequent in women than in men due to hormonal differences These diseases are treated with drugs that suppress the immune system as well as with antibodies that attack lymphocytes

Autoimmune Diseases Diabetes Mellitus (Type I or Juvenile Onset) -The immune system destroys the Insulin producing cells of the pancreas. Multiple Sclerosis -occurs when the body attacks its own neurons. -effects include the loss of motor control, feeling or even paralysis of the affected areas. -MS generally attacks the neurons of the optic nerves, the brain and the spinal cord.

Autoimmune Diseases Rheumatoid Arthritis The body’s own antibodies attack and destroy tissue at the joints The condition is chronic, with episodes of pain and swelling No cure, but patients may have joints removed and replaced by artificial ones

Immune System Diseases B. Immune Deficiencies - The inability of the immune system to protect the body from pathogens. Severe Combined Immune Deficiency (SCID) HIV/AIDS

Immune System Diseases HIV/AIDS (Human Immunodeficiency Virus) Attacks and kills Helper T Cells. Without these cells, circulating antibodies drop in number and the body is left more vulnerable to other invading pathogens.

Organ Transplants Organ Transplants and Rejection If the body receives tissue from another person or animal the body will recognize this tissue as foreign An immune response will be started against the new tissue If the immune system isn’t repressed, the new tissue will be rejected This is why organ donors are closely matched to their recipients