Immune System

First line of defense The skin serves as a physical barrier to prevent the passage of many disease-causing microorganisms. The skin is also slightly acidic and has good bacteria.

Antigens Antigens are substances that cause the immune system to attack. An example of an antigen is a surface protein of a flu virus. Cells produce antibodies to fight antigens. Antibodies destroy pathogens directly or signal immune cells that pathogens are present.,

Specific mechanisms of host resistance This specific immune response enables the body to target particular pathogens and pathogen-infected cells for destruction. It depends on specialized white blood cells called lymphocytes produced in the bone marrow . T-cells (produced from lymphocytes that matured in the thymus gland) B-cells (produced from lymphocytes that matured in the bone marrow).

Production and Maturation All lymphocytes, macrophages and red blood cells produced in bone marrow and T cells mature in Thymus and B cells stay in bone marrow to mature

T-helper These cells travel through the blood and lymph, looking for antigens –markers on foreign cells. Upon locating an antigen, they notify other cells to assist in combating the invader. T-helper cells do this through the use of cytokines (or specifically, lymphokines) which help destroy target cells – T-killer cells, activate B cells and stimulate the production of healthy new tissue. Interferon is an example of such a cytokine – one treatment of HIV which infects and kills T-helper cells.

B-cells get turned on by T-helper cells to make specific antibodies that tell macrophage to get them out of the way T-killer cells get help from T-helper cells to turn on then do the killing

Vaccines Vaccinations give the body a preview of dangerous antigens. This allows the body to develop antibodies to fight this antigen. The body is able to generate an immune response quickly to prevent the disease from doing harm to the body. Brain Pop Video

Common pathogens Pathogens cause disease. Bacteria and viral pathogens are the most common causes of human disease.

Bacteria Bacteria can also cause infections. When bacteria enters a host they are able to reproduce in large numbers and may produce toxins that affect the health of the host. The bacteria and their toxins are perceived as antigens by the body. Antibiotics can be an effective treatment for bacterial infections.

Viruses Viruses lack ribosomes and are not able to reproduce on their own. Viruses infect cells and use the cellular components to reproduce and spread to other cells.

Virus Infection

Viruses When necessary viruses are treated with anti-viral medications that prevent their reproduction within the host. Antibiotics are not effective against viruses. Examples of viruses Influenza (flu) Herpes HIV

HIV HIV attacks key cells involved in the bodies immune system. Infected individuals can not recognize antigens or are not able to mount a response. These individuals can then be killed by “harmless” diseases.