Innate vs Adaptive Immunity


The innate immune system is the first line of defense the body has against foreign particles.  It acts as a physical and chemical barrier to pathogens.  Innate immunity is non-specific and it does not provide long-lasting protection for the body.

The innate immune system is responsible for bringing in other immune cells to sites of infection in the body.  White blood cells secrete cytokines, chemical messengers, to draw in other immune cells called the complement system in order to identify the pathogen and activate specialized white blood cells (adaptive immunity) to help remove and clear the pathogen.

The innate immune system can only do so much to protect the body. It then has to activate the adaptive immune system to eradicate the pathogens.  The adaptive immune system can “remember” previous pathogens and therefore provides faster, more effective infection eradication (Murray, 2008).

The adaptive immune system is composed of T and B cells.  T cells mature in the thymus gland  and are activated by thymulin hormone, a hormone that requires zinc in its active form.  B cells recognize foreign particles, or antigens and alert other immune cells to seek out and destroy the invading pathogen.  B cells and their antibody production make the adaptive immune system highly specific to each foreign particle.

The memory cells produced after an infection allow for a faster defense if the body is exposed again because the memory cells will alert the adaptive immune system first, rather than having the innate immune system try to handle the pathogen itself before alerting the adaptive immune system.

 The innate and adaptive immune systems share two types of cells:

  • T cells (both Th1 and Th2)
  • Natural Killer T cells

Types of cells involved in Innate Immunity:

  • Dendritic cells
  • Macrophages
  • Mast cell
  • Natural Killer cell
  • Granulocyte
  • Basophil
  • Eosinophil
  • Neutrophil
  • Complement protein

Types of cells involved in Adaptive Immunity:

  • B cells and the antibodies they produce
  • T cells (CD4+ and CD8+)

How The Immune System Works:

Macrophages are the first-line of defense against bacteria or other foreign particles.  They reside in the spleen, bone marrow, lungs, and lymph.  They excrete lysozymes and proteolytic enzymes to destroy foreign particles.  Additionally, the cytokines TNF and interleukin-1 are excreted to start the inflammatory cascade around the site of infection.

Neutrophils are the second line of defense that create superoxide radicals to destroy pathogens.

The macrophages present the antigen to B and T cells so they can look for more of the pathogen throughout the body.  B cells transform into plasma cells and release large quantities of immunoglobulin(Ig) antibodies into the lymph that eventually end up in the blood stream through the jugular vein in the neck.  The activated T cells reproduce and circulate through the blood, looking to destroy the pathogens.

There are several different types of T cells.  When the innate immune system activates the T cells via antigen presentation, they differentiate into Th1 and Th2.   Th1 cells direct cytotoxic T cells to in the case of tumors or viral or bacterial infections.  Th2 cells activate B cells during the allergy response.  Helper T cells secrete cytokines (interferon, lymphotoxin, and interleukins) that warn and stimulate B cells, T cells, and neutrophils, while also stimulating both natural and cytotoxic killer cells.

The immune system also has a system of restoring balance after an infection.  Suppressor T cells secrete chemicals at the sites of infection to calm down the T and B cells.  Moreover, both B and T cells produce memory cells that circulate in the bloodstream, looking for another exposure to the pathogen that just attacked.  In this way, the immune system can mount a faster defense against the pathogen, with a higher chance of defeating it before any serious damage occurs.

The innate and adaptive immune systems work together to protect the body.  They each have different but equally important roles in keeping the body healthy and free of infection.

 

Resources:

 1. Matsen, J. (1998). The Secrets to Great Health: From Your Nine Liver Dwarves. Canada: Goodwin Books, Ltd.

 2. Murray, M. (2000).Total Body Tune-Up. New York: Bantam Books.

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