In the original, an alien creature shaped like a gigantic glob of jelly lands on Earth and begins attacking people by dissolving them.
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!
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.
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."
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.
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, http://www.pbs.org/wgbh/nova/aids/
Jim Sullivan's CELLS Alive, antibody production page. Go to http://www.cellsalive.com//antibody.htm.