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.

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.

• T-killer cells get help from T-helper cells to turn on then do the killing

B-cells get turned on by T-helper cells to make specific antibodies that tell macrophage to get them out of the way

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.