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Story summary:
Scientist grows blob-like cells that protect the body from germs by eating them.

Title - Mac: The Blob's Little Brother?

Drawing: movie projector

In 1988 Hollywood came out with a remake of a 1958 science fiction movie called "The Blob."

In the original, an alien creature shaped like a gigantic glob of jelly lands on Earth and begins attacking people by dissolving them.

In our bodies, tiny, blob-like cells called macrophages ("mack-row faghz-es") do much the same thing, except they gobble bacteria, fungi, parasites and other harmful organisms.

Macrophages--or "Macs" for short--will surround and eat germs almost anywhere they show up in the body, like at a cut or scrape.

Photo: A macrophage, a lymphocyte and Strep bacteria

Here, a human macrophage cell moves toward a bead (yellow) of Streptococcus bacteria. On top of the macrophage is another immune cell, called a lymphocyte. Photo courtesy of Jim Sullivan, CELLS Alive!

It helps to think of Macs as soldiers rushed to the front lines of war--germ warfare, that is. And like a fighting unit's radio operator, Macs also call in the heavy artillery--in this case, the immune system's killer T-cells and B-cells.

Ka-boom! --Animation of an exploding bomb T-cells destroy the body's virus-infected cells before they're forced to make thousands of new viruses.

B-cells make antibodies. Antibodies are like "smart bombs" that home in on certain proteins on germs called antigens.

Photo: Macrophage that has 'swallowed' some bacteria

Here, an animal macrophage cell has snagged a few Staphylococcus bacteria (black circles) and stuffed them inside special digestive pockets. Later, it will use the germ's proteins to recruit other immune cells to join the fight. Transmission electron microscope image by Wes Garrett, Neil Talbot, ARS.

When a Mac cell eats a germ, it wears pieces of that dead germ's antigenic proteins. It then presents them to B-cells.

"This tells the B-cells, ‘Here's the kind of antibodies you should make,'" says Dr. Neil Talbot. He's an animal health researcher at ARS' Gene Evaluation and Mapping Lab, Beltsville, Maryland.

Animated cartoon of man trying to lift a heavy trash can

Macs help the body in other ways too, especially in the clean-up department.

"They're sort of the garbage collector of the body," says Dr. Talbot. "They clean up old blood cells, proteins and other wastes."

Drawing of a boneMacs get their start in marrow, the soft material inside bones. From marrow into the bloodstream, they "spread throughout the body into all its parts--including the skin, brain and muscle," says Dr. Talbot.

Macs fight hard to protect the body. But some germs have gotten smart.

Photo of baby pig nuzzling its mama

In pigs, for example, one virus actually grabs onto a Mac cell. The pig virus tricks the Mac into making more virus copies.

In pigs (unlike the healthy ones shown here), this can cause all sorts of problems that are hard to treat.

In order to test new ways of fighting virus Mac-attackers, veterinary scientists need lots of cell samples from animal donors.

Problem is, collecting the samples means harming one animal in order to find a cure for others.

Now, Dr. Talbot may have a solution: growing hundreds of millions of Mac cells inside plastic flasks using a few drops of blood, or small tissue samples.

4 flasks filled with red, green, blue, purple liquids
Drawing of scientist holding flask containing liquid chemical

Dr. Talbot hopes other scientists will use the method since it doesn't harm the animals.

His method could also help scientists discover new ways of blocking clever germs that attack Mac cells--in pigs or even people.

-- By Jan Suszkiw, Agricultural Research Service, Information Staff.

Other interesting sources of information:

"Fighting Back, PBS Nova Online,

Jim Sullivan's CELLS Alive, antibody production page. Go to

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