Immune System (Part of Human Body Science)

The Immune System uses two ways of doing things in order to protect the body from foreign invasion.

• The innate = nonspecific defense system 2. The adaptive = specific defense system

The innate nonspecific defense system is like the low key soldier that is always prepared for foreign invasion. The “1st line of defense” = your external body membranes: skin, mucosa, digestive enzymes. The “2nd line of defense” = whenever first has been penetrated results in inflammation, fever, phagocytosis, natural killer cells, interferons, chemotaxis, and release of cytokines

This system is more like the sniper soldier equipped with high-tech weapons to attack particular foreign substances. It’s the “3rd line of defense” which will take more time to perform in the body.

The benefit is the body kills pathogens that grow better at low body temperatures.

Inflammation occurs as a response to irritating chemicals, heat, trauma, or infection by pathogens.

• Redness • Heat • Swelling • Pain

These cells produce perforins = pore-forming proteins that target cancer and virus cells. The perforins cause these invaders to lyse or rupture.

Interferons are the body’s response to a viral infection and prevent replication of the virus after 7 – 10 days. They also activate and macrophages and NK cells.

Chemotaxis is the method by which leukocytes (white blood cells) respond to damaged body tissues. This is accomplished in part through cytokines; which are chemical messengers that are released by damaged tissues.

Diapedesis is the process of white blood cells squeezing through capillary slits in response to cytokines. The process is facilitated by cellular adhesion molecules (CAMs) guiding the white blood cells to the site of damage or infection.

The adaptive response system uses humoral, or antibody-mediated and cell-mediated weapons.

Antibodies are produced that are specific for the invading antigen.

The antigen binds to B cells which are types of lymphocytes or small leukocytes. When the antigen binds to the B cells it activates the B cells to produce antibodies. Once the body has produced antibodies agianst a pathogen; it is able to recognize it in the future and destroy it more effectively.

In active immunity, an individual recieves a vaccine that stimulated an actual infection by a pathogen, stimulating the body to produce more antibodies for future protection.

In passive immunity, an individual does not produce their own antibodies, instead recieves them from another source. Example: Mother to infant through breastmilk

T cells are primarily responsible for recognizing foreign cells. A T cell is a lymphocyte that triggers the action of other lymphocytes.

In a three-step process, T cells activate other lymphocytes: #1 Macrophages capture the foreign cell #2 A T-helper cell binds to it and secretes a cytokine that signals the cytoxic T cell #3 The cytoxic T cell responds through chemotaxis and actively destroys the foreign cell