innate and adoptive immunity

Innate and Adaptive Immunity

Innate immune system

The innate immune system is the first line of defense against invaders. It is described as being non-specific and protects the body through the following mechanisms:

Physical barrier - The tight junctions between epithelial cells (of the skin) make it difficult for pathogens to gain entry into the body. In other parts of the body (nose, mouth, etc) the epithelial cell contains such protective features as cilia that trap foreign material thus preventing them from gaining entry into the body.

Chemical barriers - Such chemical factors as the acidic conditions of the digestive tract create an unfavorable environment in which some invading micro-organisms cannot survive.

Cellular responses - Unlike other cells of the immune system, those of the innate immune system are non-specific. As such, they not only respond to a range of invading microbes and material in the body, but also activate more specific cells.

Examples of cells of the innate immune system include:

· Neutrophils - Circulate in the body and destroy invading microbes by ingesting them (through phagocytosis).

· Macrophages - Can be found in many tissues in the body. They trap and destroy invading microbes through phagocytosis. They also secrete signals that recruit other cells to the affected site.

·      Dendritic cells - Found in various tissues and serve to bridge the two systems of immunity (innate and adaptive). However, they also destroy invading microbes through phagocytosis.

Natural Killer Cells - Release chemicals that destroy the invading organism.

Adaptive immunity

Also known as the acquired immune system, adaptive immune system takes over when infections get past the first line of defense. This line of defense is slower, compared to the first line of defense.

Unlike innate immunity, adaptive immunity is antigen-specific which means that cells of the adaptive immune system respond to specific molecules on the pathogen.

Cells of the adaptive immune system include:

· T cells - T-cells include: Helper T cells (activate B cells), Cytotoxic T cells (destroy infected cells), and Regulatory T cells (regulate immune response)

· B cells - Secrete high amounts of antibodies (IgG, IgA, IgD, IgE, IgM) that bind and neutralize specific microbes.

innate immunity

Innate immunity refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen's appearance in the body. These mechanisms include physical barriers such as skin, chemicals in the blood, and immune system cells that attack foreign cells in the body. The innate immune response is activated by chemical properties of the antigen.

Adaptive immunity

Adaptive immunity refers to antigen-specific immune response. The adaptive immune response is more complex than the innate. The antigen first must be processed and recognized. Once an antigen has been recognized, the adaptive immune system creates an army of immune cells specifically designed to attack that antigen. Adaptive immunity also includes a "memory" that makes future responses against a specific antigen more efficient.