That Appendix May Be Good for Something After All

You’d think life was dangerous enough without our bodies lugging around a useless structure that can turn traitor and kill us. We’re talking, of course, about the appendix--that 4-inch-long blind alley that branches from the right side of the colon. (“Vermiform appendix,” for any Latin lovers out there, means “hanging, worm-shaped form.”)

In school, kids learn that the appendix is an evolutionary vestige--one that was more important in our distant past, when our ancestor’s diets were different, but pretty much a free-loader now. Medical students learn that too.

Yet the idea has been growing for a while that the appendix does something good for us.

That “something good” must be subtle, of course. The appendix isn’t needed for life: Removing it when it gets diseased doesn’t make folks drop dead (though this may not have been the case for the first appendectomies, way back in the 1700s).

In fact, if there are any down sides to strolling around without an appendix, scientists have still to find them.

Yet the case for the useful appendix is alluring.

Even old-time anatomists noticed that the appendix had striking similarities to structures in the gut, lung and other mucus-making tissues that are loaded with cells of the immune system. And if you look at it under the microscope, the appendix is rather like a structure in the chicken called the bursa of Fabricius--and that’s definitely an immune system organ. (Immune cells were first discovered in the bursa.)

Those things add up to an interesting idea: that the human appendix plays a part in developing the body’s immunity.

If that’s the case, it would be great to carefully compare immune systems of people who’ve had their appendixes out and those who haven’t--or to study human appendixes in detail to find out just what they’re doing to immune cells.

Great but brutishly difficult, says appendix researcher Rose Mage at the National Institute of Allergy and Infectious Diseases. Try getting hold of the tissue--unless, that is, it’s a diseased appendix from an appendectomy, which means the tissue is probably not normal anyway.

The rabbit appendix is another matter (and luckily rabbits have a much heftier appendix for their body size than do we). From these, Mage’s team has learned that the appendix starts filling up with immune cells after birth until by 6 weeks it’s positively brimming with them. Thereafter, the numbers subside: Rabbit youths have relatively shrunken appendixes.

This also seems to be the case with human appendixes, to the extent that Mage can study them: They fill up with immune cells then lose them by the teenage years.

Mage has also learned that the immune cells kind of mature while they’re hanging out in the rabbit appendix--so that they’re ready to fight the good fight against bacteria, viruses and other looming threats.

“The appendix seems to be important in the very young,” she suggests. This may be why people do nicely without them. By the time they’ve gotten appendicitis, maybe the structure’s already done its job.

A few more facts about appendixes:

* The causes of appendicitis are varied, but often stem from the narrowness of the appendix’s opening to the colon. “If you get a hard piece of stool or a piece of corn, nut or debris, such as a piece of celery, that fills up the opening of the appendix so it can’t empty out into the colon,” says Dr. Bennett Roth, professor of medicine at UCLA, it can lead to inflammation, infection, even rupture.

* Inflamed appendixes may increase someone’s odds of getting inflammatory bowel disease, says Dr. Gary Lichtenstein, director of the inflammatory bowel disease center at the Hospital of the University of Pennsylvania. This again suggests the appendix has a role in immunity--though in this case, immunity run amok.

* Finally, certain surgeons have no doubts that the appendix is useful. They use it to create an artificial urine channel for kids born with urinary tract defects.

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If you’d like to suggest a topic, write Rosie Mestel at L.A. Times, 202 W. 1st St., Los Angeles, CA 90012 or e-mail her at rosie.mestel @latimes.com.