The Foolproof Guide to the Innate Immune System

[Ancora_Imparo]

By popular demand!

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The Innate Immune System

The innate immune system is the body's non-specific defense against pathogenic attack. This means that it:
1) Responds to all infections in the same manner
2) Has no memory of prior infection
3) Has a level of response that is similar at each exposure

It is just as important as the adaptive immune system mainly due to its faster speed of action. This is beneficial because it reduces the spread and damage of the pathogen very early on, however, it is usually the adaptive system that is responsible for flushing it out of the body completely. Even after the adpative system kicks in, the innate defenses still work alongside it (ie: don't think of the two systems as separate events - they co-exist). The innate immune system is also phylogenetically older than the adaptive immune system (ie: evolved earlier).

The first line of defence
1. Intact skin (must mention INTACT) - physical barrier
2. Sweat - contains salts that inhibit growth of pathogenic bacteria by drawing water from them
3. Cilia - ear and upper respiratory system
4. Secretions - acid in stomach, mucus in gut, respiratory system, urinary and  reproductive systems, tears, saliva, sebum (oil), milk
5. Natural flora - Non-pathogenic bacteria found in the body. These inhibit the growth of pathogenic bacteria by out-competing them.

The second line of defence
1) Cells
a. White blood cells - phagocytes (neutrophils: the major white blood cell involved, monocytes: become macrophages when they leave the blood stream)
b. Natural killer (NK) cells - kill virus-infected cells
[c. Antigen-presenting cells - these act as a messenger between the innate and adaptive immune system (eg: dendritic cells)]

2) Proteins
a. Complement proteins - lyse bacterial walls and then attract phagocytes
b. Interferon - proteins secreted by virus-infected cells .These prevent the synthesis of viral RNA. 
c. Cytokines - protein molecules that act as messengers between cells of the immune system

3) Processes
a. Inflammation - reddening, swelling, vasodilation (allow for more cells to gain access to site of damage/pathogenic entry, increased temperature (increased rate of reactions, thus speeding up defence process), release of histamine, formation of blood clots, phagocytosis

[ealam2]

Wow! Thanks heaps! This is a really good way for me to consolidate what I know!

[Phy124]

Very nice, keep up the great work!

(Added to advice megathread)