immune

Immunity Infectious disease is caused by an organism entering the body and multiplying inside its host.
The Immune System: Non-specific Defense: General defense that acts against anything non-self.
Mechanical barriers (first line of defense)

Skin: layers of dead cells; poisonous chemical substances; harmless bacteria.
Mucous membranes: line nasal and oral passages to trap microorganisms.

Chemical barriers

Enzymes: pathogens reaching the stomach are destroyed by powerful chemicals.
Interferon: produced by infected cells in response to viral infection.
Inflammation: reaction to tissue damage. Warmth, pain, itching, reddening, swelling. (second line of defense)

The Immune System: Specific Defense: Components of the immune system attack specific pathogens by identifying surface proteins (antigens) of the pathogen.
Primary response
T cells: attack antigens in a cell-mediated response. Some remain as memory cells to attack if the antigen is encountered again.
B cells: produce antibodies that bind to and destroy antigens.
Secondary response: memory T and B cells multiply when host is invaded again.

Natural immunity: present at birth.
Acquired immunity: developed after birth.

Active immunity: developed as a result of one’s own immune system responding to a harmful agent. Developed naturally or as a result of vaccination
Passive immunity: developed in another organism and passed on to another. Received by fetus from mother or by injection

The Lymphatic System
Lymph: fluid in lymph vessels.
Lymph vessels transport lymph to the circulatory system.
Lymph nodes: filters located along lymph vessels that remove bacteria and foreign particles from lymph. Lymphocytes destroy bacteria.
Lymphatic organs

Tonsils
Spleen
Thymus

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