Let's learn about innate immunity.
Our bodies have a number of ways to fight off pathogens.
One category of defense is called innate immunity or non-specific defense.
In innate immunity the same kind of defense is used against all types of pathogens.
Three types of innate immunity are mechanical barriers, cells and chemical mediators.
Let's take a closer look at mechanical barriers.
The keratonized or hardened cells of the skin form a natural barrier against pathogens.
The mouth is also a barrier and is lined with mucous containing lysozymes that work to destroy
pathogens.
The stomach contains hydrochloric acid that destroys pathogens.
Next we'll look at how cells form a line of defense against pathogens.
Some cells engulf pathogens.
This is called phagocytosis.
The cell engulfs the pathogen and then enzymes within the cell work to destroy it.
Inflammation is another form of innate immunity.
Signs of inflammation include heat, redness, swelling and pain.
During inflammation cells known as mast cells release chemicals that promote inflammation.
These include histamine, kinins, prostaglandins and leukotrienes.
These substances work to increase capillary permeability and promote vasodilation.
Other cells such as neutrophils are attracted to the inflamed area via chemotaxis and can
move out of the blood vessels by the process of diapedesis.
Natural killer cells are specialized immune system cells that can attack pathogens and
cause them to destroy themselves.
Pathogens undergo cell death known as apoptosis.
Let's look at chemical mediators next.
Interferons are examples of chemical mediators.
Interferons are proteins that interfere or inhibit viral replication.
Some white blood cells respond to viral infection by producing interferons.
The infected cell dies and releases the interferon.
The interferon can bind to other cells turning on antiviral protein genes.
These antiviral proteins then block viral replication within the cell.
The complement system is also a form on innate immunity.
The complement system contains 20 plasma proteins that, when activated, can kill pathogens.
There are 2 ways to activate the complement system.
One way is through an antibody-antigen connection.
This is called the classical pathway and is part of specific defense.
The other is direct activation of the C3 complement protein by a pathogen.
This is called the alternative pathway and is a part of innate immunity.
The end result of activation of the complement system is the formation of membrane attack
complexes by activated complement proteins.
The membrane attack complexes can tear holes in pathogens disabling and destroying them.
Fever is a form on innate immunity as well.
Body temperature is regulated by the hypothalamus.
Chemicals called pyrogens can elevate the temperature set point in the hypothalamus.
As body temperature rises, the liver sequesters iron and zinc which pathogens need to replicate.
Fever makes it harder for pathogens to multiply.
I hope you have learned something about innate immunity and see you next time.