An Introduction to the elementary Setup of our Immune System #1

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So let's start with a short view into history, hence the development of these essential defense mechanisms. The Innate Immune System arose roughly 1 billion years ago. It is a integral part of every multicellular organism. This term refers to all defensive mechanisms with which a living being is born and which are always present. As a consequence any protein-based innate immunity mechanisms rely on proteins encoded in the germ-line. This part of the immune system has no memory and is not specific to any pathogen. All this means that the innate immunity does not improve after exposure to pathogens and that it's response to pathogens is either immediate or triggered very fast (within minutes or hours).

The Adaptive Immune System can only be found in vertebrates and is acquired following to the exposure to pathogens. It depends on specialized "killer-cells", the so called Lymphocytes. This part of the Immune System has a memory function what means, that a second infection with the same pathogen will trigger a much stronger and also faster response of the adaptive immune system. Since the whole acquired immune system is specific, it requires a distinction of cells in "self " or "non-self " (or "foreign") to know which one should be killed by the lymphocytes. The response of the adaptive immune system in generall is much slower than the one of the innate immune system and takes days to weeks.
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So the Innate Immune System keeps you in the game, while the Adaptive Immune System adapts it's defensive mechanism in a specific way to ultimately get rid of the intruder.

Components of Innate Immunity:

anatomical (physical) barriers

• skin
• mucus membranes
• secretions (to wash, trap and inhibit growth)

physiological (chemical) barriers

• temperature (fever)
• pH (skin, stomach, vagina, etc.)
• microflora in digestive tract (commensual microbiome)
• antimicrobial substances (zinc, lactic acid, defensins and lysozymes)

"Defensins" are antimicrobial proteins. E.g. Dermicidin is an antimicrobial peptide of 47 amino acids secreted by sweat glands on the skin. Each peptide forms an amphipathic α-helix and assembles to a hollow hexameric complex which inserts into the bacterial plasma membrane, hence allows ion gradient decoupling across biological membranes what kills the affected cell.

Further very important components of the Innate Immune System are defense enzymes like Cytochrome b558, iNOS and Myeloperoxidase. These enzymes allow to trigger the so called Respiratory Burst, what is a powerful mechanism for producing reactive, therefore aggressive substances, that are toxic to cells in a nonselective way:

About 15 different cell types are involved in our immune system response, which accounts for about 8% of all our cell types!

This was a first short introduction to our immune system. I will continue with further intresting aspects in my next posts, so stay tuned and follow me.

Best,
mountain.phil28

References:
All non-cited images are taken from "Molecular Physiology" lectures at the TU Graz.