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Innate Immunity Digital Infographic

By Antonio Mestanza

What Is Innate Immunity?

Skin

The Innate Immune System

Mechanical Barriers

  • The keratinized epidermis of our skin form a strong physical barrier to most microorganisms that are outside the skin

  • While our mucous membranes provide a physical barrier in the areas where our body has opening, for example our digestive, respiratory, urinary, and reproductive tracts.

Secretion

  • Our innate immune system, also known as the nonspecific defense system, is always prepared to defend the body and responds to all types of foreign substances immediately.

  • It consists of three parts–mechanical barriers, cells, and chemical mediators. Our skin and mucous membranes make up the chemical barriers. Cells such as phagocytes and natural killers make up the cells And finally, chemical substances and the inflammatory response makes up the the chemical mediators.

In addition to serving as physical barriers, these membranes also produce protective secretions, for example the lysozyme enzyme which destroys bacteria in our saliva, the hydrochloric acid and protein-digesting enzymes of our stomach, and the sticky mucus of our digestive and respiratory passageways which allows cilia to carry out its function of trapping dust and bacteria from reaching our lungs..

Cells

What happens when our surface barriers are breached?

Our surface barriers are often breached as a result of small cuts and wounds that our body receives throughout the course of our lives, luckily for us, we have our internal defenses of the innate system! In this slide we will be covering the cells of our internal defense.

Natural Killer (NK) cells

Phagocytes

Are a unique group of lymphocytes that lyse and kill cancer cells, virus-infected body cells, and other nonspecific target cells and are found roaming our body's blood and lymph. The main distinction between NK cells and other lymphocytes is that their attacks are more

Are a type of body cell of the immune system that includes cells such as macrophages and neutrophils and are found in almost every organ of the body. Phagocytes engulf foreign particles by first binding to the particle with its cytoplasmic extensions and then pulling it inside.

spontaneous and target any virus that it detects. To kill the cell, rather than using phagocytosis, NK cells release a chemical known as perforins which disintegrates the cell's composition.

Once inside, the phagocyte encloses the particle in a vacuole and, with the help of an enzyme known as lysosome, the contents of the particle are broken down and digested.

Secretion-Our skin and mucous membranes protective secretion, for example the lysozyme enzyme in our saliva and lacrimal fluid which destroys bacteria and the stomach mucosa which secretes hydrochloric acid and protein-digesting enzymes which kill pathogens

Picture of Parts of the Human Body for Reference

Cilia-Mucus-coated hairs inside the nasal cavity trap inhaled particles preventing most pathogens from reaching our lungs and causing them to be sneezed or coughed out.

The Skin-This organ, along with our mucous membranes serve as the first line of defense against outside pathogens

Natural Killer cells- Are a defense cell that lyse and kill cancer cells and irus-infected body cells. They attack any target virus it detects, meaning it is far less picky than other lymphocytes

Antimicrobial Chemicals

&

Chemical Mediators Pt. 1

Antimicrobial Chemicals

Phagocytosis- A process used by lymphocytes to engulf foreign particles, break them down, and sometimes digest them. Once the particle has been enclosed, lymphocytes makes use of an enzyme known as lysosome in order to break down and digest the particle.

The Chemical Mediators of our innate immunity consists of essential chemicals such as the antimicrobial proteins substances as well as immune responses, most notably the inflammatory response! In this bubble we will cover the antimicrobial chemicals.

What are antimicrobial chemicals?

Antimicrobial chemicals help enhance the defense of our innate defenses by attacking microorganisms directly and also by hindering their ability to reproduce. The two most important antimicrobial proteins are our complement proteins and our interferon.

Fevers

Interferons

Complement Proteins

Our complement proteins and interferons are two of the most important antimicrobial chemicals of our innate immunity and they help enhance our defenses against pathogens and bacteria through a plethora of processes and releases such as vasodilators, opsonization, formation of MACs and more!

Our complement proteins enhance the effectiveness of both our innate and adaptive defenses and consist of 20 plasma proteins. These proteins roam the blood in an inactive state, only activated once it has become fixed onto a foreign cell such as bacteria. This fixation is known as complement fixation and it results in the formation of membrane attack complexes (MACs) which produce lesions in the foreign cell's surface which allow water to rush into and eventually burst the cell.

What is a fever and why do they occur?

We can view these newly synthesized proteins as the 'bodyguards' of the cellular machinery in the healthy cell that is responsible for cellular reproduction!

Are small proteins that are released by virus-infected cells in an attempt to help defend other body cells that have not yet been infected. These released interferon molecules diffuse and bind to the membrane receptors of nearby cells, triggering the synthesis of proteins and chemicals that interfere with the ability of viruses to multiply within the healthy cells.

Fevers are defined as an abnormally high body temperature, usually accompanied by shivering and headaches and they are the result of a systemic response to invading microorganisms.

Fevers occur due to the hypothalamus's response to the chemical, pyrogen, and this is because, while our body's thermostat is typically set at around 98.6°F, the pyrogen chemical causes an increase to the temperature set by the hypothalamus.

Additionally, when our complement proteins are activated, they release vasodilators and chemo taxis chemicals which help order and deliver defense cells such as neutrophils and macrophages to the region. Lastly, another effects that our activated complement proteins can have on targeted cells is that they make the foreign cell have sticky membranes so that they are easier to phagocytize, this process is known as opsonization.

This is important as viruses require the reproductive abilities of the healthy cell in order for them to be able to replicate themselves. This is because viruses lack the cellular machinery required to generate ATP or make proteins, meaning that their ability to reproduce solely depends on our healthy body cells!

What are pyrogens?

Pyrogens are chemicals that are secreted by white blood cells and macrophages that have been exposed to foreign substances in the body.

How do fevers help our innate immune system?

Inflammatory response- Is a nonspecific, innate response that is triggered whenever body tissues are injured and result in four common effects on the area affected– redness, heat, swelling, and pain

Fever- are defined as an abnormally high body temperature that are the result of a systemic response to indvading microorganisms. Fevers help increase the metabolic rate of our tissue cells and also help prevent bacteria from multiplying.

Mild or moderate fevers can be beneficial to our innate immunity as during a fever, the liver and spleen gather up valuable nutrients (zinc and iron) that would have otherwise been used by bacteria to multiply.

Additionally, when we have a fever, the metabolic rate of our tissue cells generally become enhanced, speeding up our recovery.

Inflammatory Response

Inflammatory Response

The inflammatory response is a nonspecific, innate response that is triggered whenever body tissues are injured. For example, it occurs in response to physical trauma, intense heat, and infection.

The Four Indicators of the Inflammatory Response, and Why They Occur!

The four most common indicators of inflammation are (1) redness, (2) heat, (3) swelling, and (4) pain.

(1) When cells are injured, they release inflammatory chemicals such as histamine and kinins that cause blood vessels dilate and blood vessels to become leaky. This would describe the red pigmentation of our skin.

(2) The dilation of our blood vessels increases the blood flow to the area, directly resulting in the increased heat of the area affected.

(3) The increased permeability of the capillaries allows plasma to leak from the blood and into the tissue spaces, causing local edema or swelling.

(4) As result of the local edema that caused the swelling is that our pain receptors in this area are activated which would explain why we feel pain. These pain receptors attract phagocytes and white blood cells to the area in a process called chemotaxis.

note: Some consider the limitation of joint movement to be an additional (fifth) cardinal sign of inflammation.

The Steps of the Inflammatory Response

(1) Neutrophils following the scent

The role of the inflammatory response is to prevent the spread of dangerous agents to nearby tissues and it does this through a three-step process.

(1) In response to the gradient of diffusing inflammatory chemicals, neutrophils enter the blood from the bone marrow and follow the blood vessel walls as they follow the 'scent' of the foreign particles.

(2) Once the neutrophils have found the strongest signal of the foreign particles, they proceed with a process called diapedesis which consists of the neutrophil flattening out and squeezing through the capillary walls.

(3) The neutrophils carry out a process called positive chemotaxis which consists of them simply continuing to gather in the area of the tissue injury. Within an hour after the injury has occurred, the neutrophils are already devouring any foreign material present.

(2) Neutrophils flattening out (diapedsis)

(3) Neutrophils gathering together

(positive chemotaxis)

While the neutrophils are going through this process, monocytes are following closely behind and eventually turn into macrophages which massively help the battle against the bacteria as they replace the short-lived neutrophils that begin to die off.

Also, while this 'war' is going on, the clotting proteins are activated to wall off the damaged area with fibrin to prevent the spread of pathogens, and this fibrin helps provide a foundation for permanent repair. The local heat caused by the number of cells increases the metabolic rate of our body cells.

Where does our Pus come from?

Pus is a mixture of dead/dying neutrophils, broken-down tissue cells, and pathogens and they may form in infected areas depending on the severity of the infection.

Abscess- When the area is not fully cleared of debris and the sac of pus becomes walled off. Requires surgical drainage

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