Innate and adaptive are words that get thrown around a lot but aren’t always clearly understood. They both appear to be universally positive, and when you hear them it is often in the context of individuals who have identified as one or the other. But the reality is that they are more like antonyms, albeit opposites on a sliding scale rather than opposing concepts.

The innate immune system is the body’s way of defense against infection. Read this in-depth blog to gain a better understanding.

What is Innate Immunity?

Innate immunity refers to the immunity that you are born with. 

It is the sum of all the body’s defense systems that are always present and ready to act immediately upon arrival of a foreign invader.

It responds rapidly but it is non-specific.

Components of Innate Immunity

The First Line of Defense

1. The Skin
   • Keratinocytes – these skin cells provide a barrier against the outside world. These cells continuously remake and slough off.
   • Sweat Glands – produce sweat that goes onto the surface of the skin. It provides skin surface with acidic pH to prevent bacteria growth. 
   • Dendritic cells – also known as Langerhans cells. They capture antigens and display them on their surface. These cells are part of the innate immune system

2. Second Line of Defense (Internal Defenses)

1. Natural Killer Cells – They have the power to destroy body cells that have abnormal or unusual plasma membrane proteins. They have the power to kill a wide range of infected body cells as well as certain tumor cells.

2. Phagocytes – are specialized cells, capable of performing phagocytosis. 

Note: Phagocytosis is when a cell ingests those microbes or other particles such as cellular debris.

Two major types of phagocytes:

1. Neutrophils
2. Macrophages

5 Steps of Phagocytosis
Chemotaxis -Phagocytes are drawn to a site of damage by a chemical attraction
Adherence -Innate immune attachment to a microbial community or other foreign particles
Ingestion – swallowing of the microbe.
Digestion – it brings that phagosome into itself and it’s going to bond with what is called it fuses with what is called a lysosome.
Killing – it is where the enzymes surround. 

3. Inflammation 

• innate response to tissue damage.
• 4 characteristics of inflammation: redness, heat, swelling and pain.
• The purpose of inflammation is that it is an attempt to dispose of whatever phagocyte microbes, toxins or any other foreign material that could be at the site of injury.

3 basic activities of inflammation

1. Vasodilation and increased permeability of the local blood vessels
   •  release histamine (increases blood vessel permeability).

2.  The emigration of phagocytes 

•  The blood vessel itself starts to stick to the inner surfaces of the blood vessels and then they can squeeze through the wall of the blood vessels to go into the damaged area.

3. Chemotaxis and microbial attack 

•  neutrophils show up first and then the monocytes. 

Prostaglandins – intensify the effects of histamine. 

Leukotrienes – it increases the permeability of the capillaries. 

Note: The more area that is damaged by the injury the greater this process is going to be. The greater the inflammation is going to be and inflammation is going to be caused by this fluid and cells going to that area.

4. Fever

• It is part of the innate response. 
• elevation of temperature either locally or systemically. 
• When the body temperature is elevated it helps these cells in the body to work much more quickly it intensifies the effects of different things like interferons it helps these cells get to these areas much quicker and then it speeds up these body reactions that are also happening as the temperature increases a little bit.
• inhibit the growth of microbes. 

5. Antimicrobial Fluid 

• It can be found in the various fluids of the body.
• discourage microbial growth.
• One such type of protein: interferons.
• Interferons – produced by the cells of the body that have been infected with a virus to INTERFERE with the viral replication in healthy cells. 
• Complement system – can be found in the blood plasma and is not normally active. 

If you pay attention to your biology, innate and adaptive immunity should be fairly straightforward. Innate immunity is the first line of defense that our bodies have against invading bacteria and viruses. This immunity is inborn, fast acting, and nonspecific. While not always successful, it does provide us with some rudimentary defense against pathogens. Adaptive immunity, on the other hand, is a little more complicated. It involves immune cells that become aware of invaders to specifically target them.

 Innate immunity cells do not need specific previous exposure to a pathogen to be activated. Innate immune cells are first responders, in other words. They act immediately when an infectious agent enters the body and lay the groundwork for further immune defenses.

To view more on the Innate Immune System, watch my video here:

Fact Sheet/ Study Guide