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Interviewee: Hidde Ploegh, Harvard Medical School.

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Produced by Jack Penland

Copyright © ScienCentral, Inc., with footage from Harvard Medical School.

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Elsewhere on the web

The Immune System - NIAID

Immune System/AIDS Topics - Library of Medicine

Show Me a DC-SIGN: Dendritic cells step into the spotlight - HIV Plus


It’s a short movie that will never make it to the big screen.

Nevertheless, it may have a big role in fighting disease.

This ScienCentral News video explains.


Smart cells

There’s a war going on over your body. Right now your body’s defenses are working to neutralize invading bacteria and viruses. Maybe you breathed them in. Maybe they got in through a wound in your skin. However they got in, those microbes are trying to multiply and take over. Fortunately for most people, the body is very good at defending itself.

But how does it all work? A study published in Nature magazine offers new information about how the body defends itself. It’s basic research that someday could lead to new ways to battle AIDS, combat organ rejection, and help the battle against other infections.

Researchers combined recently-discovered genetic techniques along with powerful microscopes to actually photograph one cell talking to another. According to Dr. Hidde Ploegh of the Harvard Medical School, "We can actually look at some of those events in a way that was not previously possible."

The chain of events works like this. At the forefront of your body’s defense system is a layer of cells called dendritic cells. Ploegh says these cells are a "rapid deployment force" against invading microbes that are "found throughout the body immediately underneath the skin very much like a coat of mail."

Scientists know that when a microbe enters the body, it will bump into one of these cells. The dendritic cells surround, absorb and chop up invading bacteria and viruses. But Ploegh and his associates were interested in what happens next.

"For us to defend ourselves against pathogens we need to recruit cells of the immune system to the appropriate location," he explains, "so that everyone gets together at the right place at the right time."

What the researchers showed was "to our astonishment…that from deep inside the cell fingers would shoot out to the contact site with the other cells (of the) immune system, as if there was almost like a secret handshake."

But before they could watch and photograph this process, they had to find a way to make the dendretic cells stand out. They took the gene that makes some jellyfish glow green and put that gene in a mouse, but in a new way so that only the dendritic cells glowed green.

Dr. Jonathan Yewdell, an immunologist at the National Institute of Allergy and Infectious Diseases pointed out that "this has never been done before in living tissue; the mouse is a living, three-dimensional map of where these dendritic cells are distributed."

The researchers then used powerful microscopes to actually watch and photograph the process happen in the mice.

Ploegh calls this basic research into how the immune system works "essential" in finding new ways to combat disease.

"We know the importance of the immune system," he says, "mostly because of what happens when it fails us." He points out that the HIV virus destroys cells of the immune system and that this research could offer new ways to fight the virus. He adds that organ transplants often fail because the immune system treats the transplant like an invading microbe and rejects it. Building on this discovery could lessen the number of rejections.

And, what about the mice? Says Yewdell, "They are very useful mice. We want them, lots of scientists will want them…they’re really cool mice."



by Jack Penland


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