Disease and the Immune System

Disease: Any change to normal body function except for injury. Some diseases are genetic PKU Sickle-cell anemia Type I Diabetes _________________________ Materials in the environment often cause disease. Cigarette smoke Chemicals Toxins

Other causes of disease Pathogens: The causes of infectious diseases. Bacteria, virus, protozoa, fungi, and parasites Not ALL species of these organisms are pathogens. Reservoir: Source of the pathogen in the environment. Animals, humans, soil, inanimate objects. Infectious disease_________________________________________________________________________________.

Spread of infectious diseases Physical contact Touch, sexual or indirect contact Contaminated food/water Infected animals Vectors

Vectors: Organisms that carry the disease Most common are ticks and mosquitoes through biting. Flies can act as a vector by landing in disease and then on humans.

Symptoms of disease When a pathogen invades it infects cells of the body. These infected cells are often ruptured, or killed. Other times toxins are produced that affect specific organs or systems. Sometimes the symptoms felt are the body’s immune system fighting back.

Disease Patterns As an outbreak of a disease spreads a number of agencies are notified. CDC and WHO monitor disease patterns Endemic disease Epidemic Pandemic

Methods of fighting disease The Immune System – natural defense Antibiotics are a method of combating infectious disease. Attack microorganism’s cells or cellular process Do not harm human cells

Immune System: 2 components. Specific and Nonspecific Immunity Nonspecific Immunity is the first line of defense. Provide a general defense against al pathogens Slows progression of disease while specific immunity kicks in Barriers: Prevent pathogens from entering the body Skin – physical barrier Layers of dead skin cells and waxes coating the living cells beneath. Chemical – attacks incoming pathogens Saliva, tears, mucus contain enzymes (lysozyme) that attacks and destroys bacteria cell walls. HCl in the stomach kills bacteria if they enter

Nonspecific Response Cellular defense – A type of White Blood Cells (WBC) called macrophages undergo phagocytosis. Interferon – cells infected with a virus secrete a protein called interferon which stimulates neighbor cells to make antiviral proteins.

Inflammatory response Damaged tissue and invading cells release proteins which allow for WBCs to get to the area.

Specific Immunity – Involves Lymphatic System The lymphatic system filters blood and lymph and destroys microorganisms. Destroys fat Lymph is a clear fluid that bathes body cells and is collected by lymph vessels.

Lymphatic Organs Each of the following organs is made of lymph tissues, lymphocytes, and connective tissue. Lymph nodes Tonsils Spleen Thymus

Components to the Immune System Macrophages – phagocytosis Helper T Cells – activate B and cytotoxic T cells B Cells – Create antibodies and memory cells Cytotoxic T Cells – direct attack on invading pathogens

Specific Immunity – B Cell Response B Lymphocytes are found in all lymph tissue. They have the role of being antibody factories. Antibodies are proteins made by B lymphocytes that target specific foreign antigens. Antigens are anything foreign to the body that cause immune responses.

B Cell Response Macrophages present antigens on their surface. This antigen is called a processed antigen. The macrophage then binds to a helper T Cell (Another type of lymphocyte). The helper T Cell is now considered “activated”.

B Cell Response The activated helper T Cell go on to activate B cells and cytotoxic T cells. When activated B Cells divide and mature into plasma cells and are given instructions to make specific antibodies to the antigen found. The activated B cell creates the active plasma cell and memory cells.

B Cell Response The antibodies attach to the foreign antigen and cause clumping, making it easy for macrophages to destroy them

T Cell Response The helper T cells also activate cytotoxic T cells. 1. These cytotoxic T cells release cytokines which signals the immune system to activate. 2. The cytotoxic T cells also directly attack pathogens and destroy them.

Types of Immunity Primary Response – first response to an invasion in the body. Passive Immunity – A form of temporary protection against a pathogen. The antibodies are made by other humans/animals and injected into the infected patient. Done for people exposed to rabies, tetanus, hepatitis and venoms. Also done by pregnant mothers, passing antibodies through the placenta to the developing fetus.

Types of Immunity Active Immunity – The memory cells produced by B cells maturing are involved in long-term memory of pathogens. This type of immunity is a result from a previous infection OR immunization. Immunization is when a weakened/dead strain of a pathogen is injected into the body so that a first response can occur

Booster Shots After the first injection antibodies are made. A second injection is made to further boost the amount of antibodies/memory cells made.

Immune System Failure Certain disease attack the immune system directly. HIV is a virus that infects helper T cells. These T cells become HIV producing factories. As a result the immune system cannot fight other diseases over time.