The Immune System

Life Science - Middle School

The Immune System & Disease © C opyright NewPath Learning. All Rights Reserved. 94-4905 Images courtesy of NIH pathogen phagocyte stomach salivary glands Our body has created barriers known as the rst line of defense to keep the pathogens out. The skin, mouth, stomach, and breathing passages are such barriers that trap and kill most of the pathogens that we come in contact with on a daily basis. The nose, trachea, and bronchi all contain mucus and cilia that trap and remove pathogens. Pathogens that are swallowed are destroyed by saliva in our mouth or acid in the stomach. An infectious disease is a disease that can be spread from one organism to another. Many infectious diseases are caused by organisms that are too small to see without a microscope. The organisms that are the cause of diseases are called pathogens. Each pathogen causes a specifi c disease. The major groups of pathogens that cause disease in humans are protists, fungi, bacteria, and viruses. Noninfectious diseases are diseases that are not spread from one person to another, such as diabetes, allergies, and cancer. The second line of defense is a response to damaged tissue called the infl ammatory response. The infl ammatory response causes the body to release chemicals and white blood cells into the tissue near the injured area so that the chemicals and white blood cells can ght the invading pathogens. The response is the same no matter what the invader is. The white blood cells involved with the infl ammatory response are called phagocytes. A phagocyte is a white blood cell that surrounds the invading pathogen and breaks it down. The area that is affected by an infl ammatory response becomes red and swollen because the blood vessels widen to allow the uids and blood to get to the injured site. 1 2 T cell T cell T cell T cell B cell B cell bacteria fungi protist virus Body Defenses and Disease trachea bronchi phagocyte engulfs and destroys bacteria inflammatory chemicals released infection site bacterium blood vessel becomes more permeable white blood cells migrate into surrounding tissue 1. T cell recognizes a virus by its antigens. T cell divides over and over, creating new T cells that also recognize the antigen. antigen virus 2. Some T cells attack damaged cells directly and destroy them. 3. Some T cells activate B cells to make antibodies. 4. Antibodies destroy viruses. antibody infected cell lung nose skin The third line of defense is called the immune response. An immune response is part of our body’s disease ghting system, also known as the immune system. The immune system can tell the difference between various pathogens, so that they are specifi cally targeted. The white blood cells involved with the immune response are called lymphocytes. There are two types of lymphocytes called T lymphocytes (T cells) and B lymphocytes (B cells). T cells identify exactly which pathogens have invaded the body. Each type of T cell recognizes one pathogen. What the T cells actually recognize is something called an antigen that is on the pathogen. Different antigens have different chemical structures. T cells can distinguish these differences. B cells are lymphocytes that produce chemicals, called antibodies, which help to destroy the different types of pathogens. Some antibodies will attach to the antigens causing the pathogens to clump together. This makes it easier for phagocytes to detroy them. Other antibodies prevent the pathogens from attaching to body cells. antibody 3
The Immune System & Disease Photos courtesy of NIH antibody lung antigen noninfectious disease bacteria pathogen barrier phagocyte bronchi protist B lymphocyte salivary gland fungi trachea immune response T lymphocyte infectious disease virus infl ammatory response white blood cell Key Vocabulary Terms © C opyright NewPath Learning. All Rights Reserved. 94-4905 The Immune Response What is the rst line of defense? ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ What are pathogens? ____________________________________ _______________________________________________________ What is an infectious disease? _____________________________ _______________________________________________________ What is a noninfectious disease? __________________________ _______________________________________________________ What is the third line of defense? ______________________________________ ______________________________________________ ______________________________________________ ______________________________________________ ______________________________________________ ______________________________________________ What is the second line of defense? ______________________________________________________________ __________________________________________________________________ __________________________________________________________________ 1 2 3 T cell T cell B cell Body Defenses and Disease What is the function of the T lymphocytes (T cells)? ____________________________ ____________________________ What is the function of the B lymphocytes (B cells)? ____________________ ____________________ ____________________ ____________________ What is an antigen? _______________ ________________________________ What is an antibody? _____________ ________________________________ \|xiBAHBDy01782qzZ