Immune System First Line of Defense, don’t let em in

Surface Barriers Surface Barriers or Mucosal Immunity The first and, arguably, most important barrier is the skin. The skin cannot be penetrated by most organisms unless it already has an opening, such as a nick, scratch, or cut.

“fly paper” Mechanically, pathogens are expelled from the lungs by ciliary action as the tiny hairs move in an upward motion; coughing and sneezing abruptly eject both living and nonliving things from the respiratory system; the flushing action of tears, saliva, and urine also force out pathogens, as does the sloughing off of skin. Sticky mucus in respiratory and gastrointestinal tracts traps many microorganisms

“Burn em” Acid pH (< 7.0) of skin secretions inhibits bacterial growth. Hair follicles secrete sebum that contains lactic acid and fatty acids both of which inhibit the growth of some pathogenic bacteria and fungi. Areas of the skin not covered with hair, such as the palms and soles of the feet, are most susceptible to fungal infections. Think athlete's foot.

“Enzymes” Saliva, tears, nasal secretions, and perspiration contain lysozyme, an enzyme that destroys Gram positive bacterial cell walls causing cell lysis. Vaginal secretions are also slightly acidic, while spermine and zinc in semen destroy some pathogens. Lactoperoxidase is a powerful enzyme found in mother's milk that starves bacteria for oxygen.

Digest em The stomach is a formidable obstacle insofar as its mucosa secrete hydrochloric acid (0.9 < pH < 3.0, very acidic) and protein- digesting enzymes that kill many pathogens. The stomach can even destroy some drugs and other chemicals.

Cause we all like flowers Normal flora are the microbes, mostly bacteria, that live in and on the body with, usually, no harmful effects to us. We have about cells in our bodies and bacteria, most of which live in the large intestine. There are 10 3 –10 4 microbes per cm 2 on the skin (Staphylococcus aureus, Staph. epidermidis, diphtheroids, streptococci, Candida, etc.).

Foot soldiers Various bacteria live in the nose and mouth. Lactobacilli live in the stomach and small intestine. The upper intestine has about 10 4 bacteria per gram; the large bowel has per gram, of which 95–99% are anaerobes (An anaerobe is a microorganism that can respire organic material (food) without oxygen (often E-Coli). These bacteria will combat foreign bacteria in your system (botulinum, salmonella, etc.)

Immune System II White blood Cells

What are they A white blood cell is also called a leukocyte They are specifically designed to help protect the body from foreign invaders (antigens). These blood cells travel through the lymph and blood streams as an important part of the body's immune systemtravel They are generally ameoba like, and some can even “crawl” around the moist tissues inside you lungs, nose and intestines

Where are they produced Leukocytes are produced in organs that have been nicknamed the lymphoid organs. These areas include the spleen, thymus and bone marrow. These areas produce and store leukocytes to prepare for an infection. Leukocytes can also be stored in other areas of the body such as the lymph nodes. Leukocytes can be broken down into two basic types, phagocytes and lymphocytes.

Phagocytes Phagocytes are formed in the bone marrow and sent throughout the body in ready defense of a foreign invader. Once created they can mature into one of five different phagocytes: monocytes, macrophages, neutrophils, dendritic cells and mast cells. Each type of phagocyte has a little different function, but all phagocytes work by consuming invading antigens and killing them. Phagocytes are formed on a regular basis in the bone marrow and are constantly present in the blood and lymph stream.

Lymphocytes Lymphocytes are leukocytes that are formed in the bone marrow when an infection occurs. From their initial production in the marrow the lymphocytes can mature into one of two types B cells and T cells

B Cells The first type, B cells, mature in the bone marrow and then are sent to circulate through the blood and lymph system. Once these cells come into contact with an antigen (foreign substance or disease) create an antibody to fight the invader, usually by surrounding and trapping it until another white blood cell can find and consume.

T cells The second type, T cells, are produced in the bone marrow as well, but they are sent off to the thymus gland to mature. Here they become involved in cell-mediated immunity. This means that they develop the ability to attack your own cells that have been infected by a bacteria or virus. T cells that are too aggressive and begin to attack the healthy cells of the thymus gland as they mature are destroyed by the thymus.

Immune System Part III Inflammation……. Burn baby burn

Trigger When an infection or other agent (acids, toxins, radiation, etc.) causes damage to body tissue it triggers inflammation. Inflammation is characterized by four signs: – redness – Pain – Heat – Swelling In some cases loss of function may occur

Purpose Inflammation has three purposes: – Increase immune response to destroy infecting agent if possible – If destruction is not possible confine the agent and limit its affects on the rest of the body – Repair or replace damaged tissue

How does your body know If an infecting agent begins to damage tissue the damaged cells release stored chemicals. Mast cells in particular are very common in the connective tissues of skin and respiratory system. They produce and store histamine and leukotrienes. When damaged they release these chemicals to promote vasodilation and increase permeability respectively. Other chemicals are involved as well

Stages Inflammation has three main stages: – Vasodilation – Phagocyte migration – Tissue repair

Vasodilation Vasodilation is the increase in size (dilation) of blood vessels. This initially allows increased blood flow to the infected area to bring phagocytes, clotting material and repairing materials, as well as remove toxins and damaged material. Vasodilation is usually assisted by an increase in permeability of the blood vessels to allow faster movement of phagocytes and materials.

Margination if you can’t beat em contain em If the infection isn’t brought under control quickly blood clotting material creates a barrier around the infected area. This blood clot barrier not only contains the infection but now slows the blood flow by the area so as to decrease nutrients going in and toxins coming out of decrease the area, and promotes phagocyte migration in the area

Tissue Repair Repair begins by the tissue even while the infection is underway, but can not complete until the infection is gone. Different tissues have different abilities to regenerate. Your skin and liver remain highly regenerative throughout most of your life while some organs like your heart and brain have quite limited regenerative properties

Assignment Page 681 # 1,2 Page 686 # 1,2

Immune System Quiz Be able to: – List 5 “first line defense” mechanisms your body uses to keep infectious agents out. – Identify the role of phagocytes, B-cells and T-cells – Discuss the three purposes of Inflammation