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Appendix - The immune system, how does it work?

Introduction

To understand both:

  • the role of the immune system in protecting us from infectious disease
  • the inappropriate overreactions of the immune system which cause allergic and autoimmune diseases

requires some understanding of how the immune system works.  The following is a simplified explanation of what, in reality, is a very complex system.

The immune system is a network of organs, cells, antibodies and chemicals. Its basic function is to prevent and eliminate infections. There are 2 parts to the system – innate and acquired immunity.

Innate immunity  - the first line of defence against invasion.

This system is always present in the body and defends us against any foreign agent regardless of type, species etc.  i.e. it is non specific

Acquired immunity  - the second line defence system against infection which creates a response specific to the invading substance.

When novel substances enter the body, they are recognised as ‘foreign’.  The body needs to be able to  recognise the difference between its own tissues and these foreign invaders. This ‘learning’ process is particularly important in the early stages of life, e.g. in the womb and shortly after birth

Substances recognised as foreign  by the immune system (bacteria, viruses, fungi, parasites , pollen, dust  mites etc) are called antigens