35.2 Defenses Against Infection Texter

The section of pages that you should have read were section 35.2, pages 1014 to 1019. The book talked about how your body protects yourself from infectious diseases.

The first barriers of defense your body has for protecting you from disease is your skin. Your skin is a thick barrier that keeps most of the diseases out of your body. But, microbes can still find ways into your body through your eyes, nose and mouth. Fortunately, they too have their own way of defending you. Your eyes protect you by using lysozyme, which is an enzyme that breaks down bacteria cell walls. The nose creates mucus that traps pathogens and your stomach acid kills most of the things that you swallow. If a pathogen doe enter your body the immune system uses its secondary line of defense that includes raising your body temperature (fever), inflammation response and interferons.

The inflammatory response is when infected areas becomes inflamed and painful because of histamines which cause increased blood flow to the infected area. When this occurs the amount of white blood cells in the area greatly increase because they are destroying the invading bacteria. Interferons are certain cells that interfere with virus growth by producing proteins that don’t allow the viruses to grow. A fever is your body’s way of slowing down or stopping the growth of pathogens. It is caused when the immune system releases certain chemicals that increase body temperature.

The immune system defenses distinguish your body’s own cells from harmful other cells. A healthy immune system recognizes its own cells and knows that they are not harmful. Your immune system also recognizes harmful cells. When a harmful cell invades your body your body attacks it and then remembers it so that if it ever attacks again your body will recognize it faster, this is known as immune response. Antigens are a foreign substance on a harmful cell that the immune system recognizes and tags to be destroyed. When it senses antigens it increases the amount of cells that kill the invaders. Antibodies tag antigens for destruction. Each antibody is made specifically for one type of cell only.

B-lymphocytes are cells that travel to the invasive cells and are created in red bone marrow. T lymphocytes are the cells that are made in the bone marrow but mature in the endocrine gland. They work together to locate and destroy invasive cells. The humoral immunity depends on the response activated when antibodies embedded on B cells hold onto antigens of invading cells. An antigen binds to an antibody and then waits for a T cell to stimulate the division of the B cells.

Plasma cells produce antibodies that are moved throughout the bloodstream. These antibodies float around and mark cells of pathogens. Healthy adults produce around 10 billion different types of antigen that allows the immune system to respond to virtually anything that enters the body. Memory B cells are the cells that remember the pathogen that the body fought off. After an infection is gone the plasma cells that destroyed it die. The memory B cells remember it and if it ever comes back it will know which plasma to make. In the long term it allows your body to build up immunity to it.

Cell mediated immunity guards the body against viruses, fungi, and single celled pathogens that take over and use the bodies own cells. It also protects the body from itself if any of its cells become cancerous. If a cell is infected with a pathogen the cell displays a little of the antigen on the outer surface and marks it to be destroyed.

This activates cytotoxic T cells, which hunt down the infected cells and kill them by puncturing their membranes or apoptosis. The memory T cells help the immune system detect if the same pathogen enters the body again. Suppressor T cells help the immune system stay in check once the infection is under control and also inhibit autoimmune deficiencies. Although cytotoxic T cells are useful to the body, they make organ transplants difficult because they recognize the organ as not itself and it tries to attack it. This is why organ transplant patients usually have to take medications the rest of their lives.

Now that you read this you should have a good idea about how the immune system works, and what it does. Thank you for reading. 8^th Period Mr. Paek’s BIO Rocks!!!!!!!