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Innate immune system

Toll-Like Receptors [TLRs] and PAMPs

Innate Immune System

First-line defence

What is innate immunity?

  • Innate immunity is a multi-level inborn defence system that is the most ancient of immunologic responses in vertebrates [and other organisms].
  • Innate immunity provides the immediate response necessary to fight off pathogens or toxic elements. It is the first line of defence.
  • Innate immunity is non-specific and has no immune memory like adaptive immunity.

Innate immunity can activate adaptive immunity

  • Adaptive immunity is much more recent on the evolutionary scale, found in jawed vertebrates and is complementary to the innate system.
  • Adaptive immunity is activated by antigen presentation by Antigen Presenting Cells [APCs] and adaptive immunity unlike innate immunity leads to long-lasting protective immunity.
  • γδ T cells [gamma/delta] T-cells are at the border between innate and adaptive immunity as these cells help with immune memory but they also have Pattern Recognition Receptors [PRRs]

  • It is said that because innate immunity has developed over millions of years, it is nearly flawless* whereas biological mistakes occur with adaptive immunity.
  • Two cell lineages play very important roles in the innate system – natural killer [NK] cells and dendritic cells [DCs] – the dendritic cells are a part of the antigen presenting cell system [APC’s] that process antigens for presentation to the adaptive immune system. A stylized graphic of a dendritic cell with its extensions [dendrites], is shown above.
  • The innate immune system depends on cytokines for destruction of potential threats such as microorganisms and these cytokines [tumour necrosis factor TNF, interferons, chemokines, interleukins] can cause extensive tissue damage and left unchecked, may stimulate autoimmune responses in the body. The innate immune system is thus under strict control in the body3.

  • Click the graphic above to view a tutorial that will provide more details about the innate immune system and how Toll-Like Receptors [TLRs] recognize Pathogen-Associated Molecular Patterns (PAMPs) to initiate chemical responses to pathogenic threats. 

Link to Immune System References

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Toll-Like Receptor