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Cell vs. virus: A battle for health - Shannon Stiles


Cell vs. virus: A battle for health - Shannon Stiles

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All living things are made of cells. In the human body, these highly efficient units are protected by layer upon layer of defense against icky invaders like the cold virus. Shannon Stiles takes a journey into the cell, introducing the microscopic arsenal of weapons and warriors that play a role in the battle for your health.

Lesson by Shannon Stiles, animation by Igor Coric.

Bacteria vs virus


The Immune System

This video describes the Immune System and explains how it detects and attacks any foreign organism that enters the body.

We learn how the team in the MRC Centre for Transplantation at King’s College London have developed a way to harness the power of the Immune System after a transplant, whilst maintaining the body’s capacity to resist infectious diseases.

Produced by Figment Productions.

How Ebola Virus Infects a Cell

This 3-D animation shows how the Ebola virus exploits a naturally occurring protein in our cells called NPC1 to cause infection and spread in the body. Narrated by Kartik Chandran, Ph.D., professor of microbiology & immunology at Albert Einstein College of Medicine. Link to full video:


How do viruses jump from animals to humans? - Ben Longdon

Discover the science of how viruses can jump from one species to another and the deadly epidemics that can result from these pathogens.


At a Maryland country fair in 2017, farmers reported feverish hogs with inflamed eyes and running snouts. While farmers worried about the pigs, the department of health was concerned about a group of sick fairgoers. Soon, 40 of these attendees would be diagnosed with swine flu. How can pathogens from one species infect another, and what makes this jump so dangerous? Ben Longdon explains.

Lesson by Ben Longdon, directed by Cabong Studios.

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Immunology wars: Monoclonal antibodies

Our immune systems are at war with cancer. This animation reveals how monoclonal antibodies can act as valuable reinforcements to shore up our defences – and help battle cancer.

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Viruses (Updated)

Explore the lytic and lysogenic viral replication cycles with the Amoeba Sisters! This video also discusses virus structures and why a host is critical for viral reproduction. Expand details for table of contents and further reading suggestions! This updated video replaces our older virus video from 2013.

Table of Contents:
0:29 Intro to a Virus
1:10 Virus Structure
2:30 Lytic Cycle
3:41 Lysogenic Cycle
4:48 HIV
5:52 Viruses in Gene Therapy, Pesticide

We cover the basics in biology concepts at the secondary level. If you are looking to discover more about biology and go into depth beyond these basics, our recommended reference is the FREE, peer reviewed, open source OpenStax biology textbook:

Further Reading Suggestions:

Learn more about the Nuclear Polyhedrosis Virus (NPV)- a virus that can target pest insects.

How does Gene Therapy Work? (from NIH)

We received a great comment asking about how viral DNA may go undetected. Check out this great journal article:


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The Amoeba Sisters videos demystify science with humor and relevance. The videos center on Pinky's certification and experience in teaching biology at the high school level. For more information about The Amoeba Sisters, visit:

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Cell vs Virus

Virus Wars

All cellular life, including you, is in an ancient and unending war with viruses. Watch how viruses attack cells and learn about RNA interference, one of the ways that cells fight back.

Play the RNA Lab:

Find discussion questions for this video and other resources in the RNA Lab collection on PBS LearningMedia:


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The Immune System Explained I – Bacteria Infection

Every second of your life you are under attack. Bacteria, viruses, spores and more living stuff wants to enter your body and use its resources for itself. The immune system is a powerful army of cells that fights like a T-Rex on speed and sacrifices itself for your survival. Without it you would die in no time. This sounds simple but the reality is complex, beautiful and just awesome. An animation of the immune system.

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Why you are still alive - The immune system explained

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Virus Rapidly Evolves To Fight Bacteria

Michigan State University researchers have seen for the first time that the Lambda virus can mutate in a short time (4 mutations in just 12 days) and found new ways to attack host cells.

Using Cancer To Fight Cancer | Vikki Academy

T-cells are white blood cells that help defend our bodies - they are equipped to identify foreign threats. But cancer cells have the ability to trick white T-cells by sending proteins that suppress them.

What can science do to provide us with a better fighting chance? Watch and learn!


A pricked finger means the immune system is hard at work. An important part of the innate immune system, the skin – has been breached, and bacteria are entering the body. The first immune cells they encounter are mast cells and dendritic cells. These cells can distinguish self from non-self thanks to the recognition of pathogen-associated molecular patterns, or PAMPs, which are molecules associated with pathogens. This recognition is not specific to any invader, but rather identifies a general attribute common to pathogens. This recognition is thanks to their pattern recognition receptors, or PRRs. The PAMPs they recognize can include bacterial lipopolysaccharides. Now that microbial components have been recognized, the body springs into action, and the inflammatory response is initiated.
The mast cells stay on the battlefield, releasing histamine and heparin. Histamine causes vasodilation of nearby blood vessels and heparin is an anticoagulant. The result is increased blood flow to the infected area, which allows more white blood cells to get there. The mast cells also release cytokines, which are cell signalling proteins that affect the behaviour of nearby cells. In this case, the cytokines are used to call macrophages and neutrophils to the area.
Neutrophils are the most abundant white blood cells. They release cytokines as well, amplifying the inflammatory response. They attack pathogens in three ways – phagocytosis (engulfing pathogens – and they can ingest up to 20 each), degranulation (release of soluble antimicrobials), and the release of neutrophil extracellular traps, or NETs. NETs are primarily composed of the neutrophils’ DNA and bind pathogens. This binding occurs thanks to positive charged proteins on the bacteria’s surface interacting with negatively charged chromatin fibers.
Dendritic cells engulf antigens – foreign substances that elicit an immune response – and break them up into smaller pieces called epitopes. Dendritic cells in the epithelial tissue move out of t he infected area and into the lymph nodes.
The innate immune system has non-specific means of intruder identification and resistance. However, when the dendritic cells enter the lymph nodes, they link the innate immune system to the adaptive immune system. The adaptive immune system consists of T cells and B cells, and brings in anti-pathogenic weaponry specific to the attacker.
T-cells are produced in the thymus, differentiating into four types: helper T-cells, cytotoxic T-cells, regulatory T-cells, or Tregs, and memory T-cells.
T-cells are specific to one antigen. After leaving the thymus, they circulate the body until an APC presents an antigen that matches their T-cell receptor, or TCR. Following this initial activation, the T-cell’s CD4 or CD8 molecule also binds the MHC of the APC, stabilizing the connection. Helper T-cells and cytotoxic T-cells also need secondary signals, as well as cytokines to become fully activated. Following these signals, the T-cell begins to divide rapidly and moves to the site of inflammation to fight the pathogen. At the infection site, mast cells, neutrophils, and epithelial cells can produce cytokines to induce further activation and proliferation of the T-cells.
Immature B-cells can be activated either by attaching to a free-floating antigen or thanks to helper T-cells or dendritic cells that present an epitope matching their B-cell receptors, or BCRs. BCRs consist of a membrane bound antibody, which is a large, Y-shaped protein that bind antigens, CD79A and CD79B. The B-cell receptor and antigen undergo cell-mediated endocytosis.
Recognition of an antigen stimulates B-cells to proliferate, and the activated B-cells undergo clonal expansion. As they proliferate, these many clones undergo somatic hypermutation. AID introduces point mutations into the clones. For some clones, this results in an increased affinity to the antigen, while for others, this means a decreased affinity. The antigen is proteolytically broken down and an epitope is then displayed on the B-cell’s surface, attached to an MHC class II protein. Before the B-cell can do anything, a helper T cell with a complementary TCR, and CD4+ glycoprotein must bind the antigen. The T helper cell then releases cytokines that let the B-cell take the next step. This is a safety mechanism to prevent accidental activation of the B-cells. The B-cells that have decreased affinity then undergo apoptosis, while the B-cells with increased affinity differentiate, becoming either a plasma cell, or a memory B-cell. The plasma cells produce antibodies matching their BCRs into the blood and lymph. Meanwhile, the memory B cells store antibodies in case of future reinfection.
When antibodies bind antigens, they label them for destruction by cells such as macrophages and neutrophils. B-cells mediate your humoral immune response, so called because it involves substances in your body fluids.

What are viruses | Cells | Biology | FuseSchool

In this video we are going to look at what viruses are.

Viruses are a type of microorganism. They are too small to be seen with the naked eye: much smaller than bacteria, and about 100 times smaller than human cells. They come in many different shapes and are present wherever there are cells to infect. In fact, viruses are the most common biological unit on Earth, outnumbering all other types combined!

Viruses can infect humans, all animals, plants and even bacteria.

Viruses are very simple. They are made up of a protein coat surrounding a strand of genetic material. The genetic material can either be DNA or RNA.

Sometimes a membrane called an envelope surrounds a virus particle. This envelope isn’t made by the virus, but is actually stolen from the membrane of the host cell. This is a great strategy by the virus - it makes it harder for the host cell to identify the virus as foreign.

As we just saw, viruses aren’t made up of cells. In fact, they aren’t really living. They are halfway between a living organism and a chemical. Because they aren’t living, we say there are different types of virus… rather than saying different species of virus. Some common types of viruses are influenza and HIV/AIDS.

So if viruses aren’t living, how do they cause illness?

Viruses are parasites: they can only reproduce in other living cells. They enter a host cell and hijack the host’s genetic machinery. They make copies of their own viral genetic material instead, and produce lots more virus particles. After lots of virus particles have been made, the host cell dies and the viral particles are released to infect more cells. The released viral particles can also spread to other people.

There are actually two different ways in which the virus attacks the host cell, which we will look at in more detail in this video. ( How viruses cause illness ).

Viruses causes many human diseases, including colds… influenza… rabies… yellow fever… HIV/AIDS… pneumonia... bird flu… zika… ebola… and the cancer causing HPV. These are just a few examples.

Fortunately, the human immune system is very good at dealing with viral invaders.

Sometimes our immune system will recognise the virus as an intruder and will destroy the virus before it gains entry into a cell. Even after infection begins, often our immune system destroys the virus and the person recovers. Sometimes the immune system cannot destroy the virus fast enough, and the virus can cause permanent damage or death. In 1918 the Spanish flu is thought to have caused up to 50 million deaths worldwide.

Scientists have developed vaccinations against lots of viruses, which have even led to the eradication of some viruses like smallpox as all human hosts became immune. However, some viruses like HIV have proved impossible to develop any kind of vaccine for.

Did you know that antibiotics do not work for viruses? They are only for bacterial infections. If you have a cold or the flu, you shouldn’t be taking antibiotics - they won’t make a difference.

There are some anti-viral drugs that have been developed, such as one that dramatically prolongs the life of people affected by HIV.

So there we have viruses. They are incredibly simple organisms, but are extremely effective at causing infection!

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What is a virus? How do viruses work?

What is a virus and how do they work? In the first video in the series, WinchPharma Science & Health look at viruses, how they infect cells and reproduce, as well as some of the practical uses they have.

Flu Attack! How A Virus Invades Your Body | Krulwich Wonders | NPR

When you get the flu, viruses turn your cells into tiny factories that help spread the disease.

Subscribe to NPR!

In this animation, NPR's Robert Krulwich and medical animator David Bolinsky explain how a flu virus can trick a single cell into making a million more viruses.

See and hear the rest of the story on

Credit: Robert Krulwich, David Bolinsky, Jason Orfanon

A Virus Attacks a Cell

The beginning of infection. Learn more at

How White Blood Cells Work

The white blood cells are an important part of our body's immune system.
Neutrophils are a special group of white blood cells that play an extremely important role in protecting the body against infections.
Mature neutrophils do not divide. New neutrophils are constantly formed in the bone marrow where they develop and mature.
Mature neutrophils are released into the blood where they circulate for 3 to 12 hours and then move to other tissues, where they survive only 2 to 3 days.
These mature neutrophils can be found in large and small blood vessels, as well as in the tiny capillaries in different tissues.
In the bloodstream, neutrophils act as surveillance cells searching for infections.
Neutrophils can sense a site of infection because of chemicals that are released by the bacteria.
Upon detecting these chemicals, neutrophils slow down and begin to stick to the walls of the blood vessel.
They then squeeze between the cells of the blood vessel wall and enter the infected tissue.
Here, the neutrophils crawl towards the infection as they continue following the chemical signals.
At the site of infection, bacteria are coated with antibodies of the immune system and marked for ingestion.
The neutrophil recognizes the marked bacterium, engulfs it into its body, ...
And traps the bacterium in a sac called a phagosome.
The neutrophil contains pouches called lysosomes, which are full of digestive enzymes and chemicals that can kill bacteria.
The pouches or lysosomes then combine with the phagosomes containing the bacteria and release the enzymes and chemicals, ...
Resulting in the ultimate death of the bacterium inside the neutrophil.
After killing and digesting the bacteria, the neutrophil is spent.
Having completed its duty, the neutrophil shrinks in size and breaks up into smaller pieces that can be recognized and eaten by other cells.

Virus VS. Cell

My science project

Bacteria and viruses - What is the difference between bacteria and viruses?

In this animation, the differences between bacteria and viruses are explained. How does a bacterium or virus enter the body? And what are typical complaints of a viral or bacterial infection? Finally, the different treatments for bacterial and viral infections are mentioned.

Health TV makes complex medical information easy to understand. With 2D and 3D animations checked by medical doctors, we give information on certain diseases: what is it, wat are the causes and how is it treated? Subscribe to our Youtube channel and learn more about your health!

Healthchannel attempts to make complex medical information easy to understand. With 2D and 3D animations checked by medical doctors, we give information on certain diseases: what is it, wat are the causes and how is it treated? Subscribe to our Youtube channel and learn more about your health!

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