The irony, Joshua Maloney said yesterday, is that he served two tours of duty in Iraq as a Marine combat engineer "and I never even caught a cold."

Then, while setting up a training exercise at the Marine Corps Base Quantico in Virginia on Jan. 31, 2007, the Bethel Park native was holding a quarter-stick of TNT in his right hand when it accidentally exploded.

That is what led him to become the first patient ever to receive a hand transplant at UPMC, and only the sixth to get one in the United States.

At a news conference at UPMC Montefiore yesterday, Mr. Maloney's doctors said he has shown no signs of rejection in the 18 days since his surgery and is making good initial progress in his therapy and treatment.

The transplanted hand came from an 18-year-old West Virginia man who died of head trauma, said Susan Stuart, president and CEO of the Center for Organ Recovery & Education. The man's family also donated his liver, kidneys and some tissue.

With his right arm in a sling and his new hand in a flexible splint, Mr. Maloney said he had thought a lot about his donor.

"Honestly, I'm going to be 25 years old this month, and it's terrible that somebody 18 years old is dead. But he was a good enough person to be willing to donate and help other people. I feel for his mother. I say my prayers and I thank God for him and ask God to watch over his mother. What else can you do? I appreciate what he did."

Mr. Maloney can wiggle his new fingers slightly, but has no sensation in the hand, and won't for months to come, said his chief transplant surgeon, Dr. W.P. Andrew Lee.

Even though the bones, tendons, blood vessels and major nerves of the new hand and Mr. Maloney's arm have been connected, the internal nerves that will control the fine muscle movements of the transplanted hand still have to extend into the tissue from his arm, and they grow at a rate of about one inch per month, Dr. Lee said.

There have been about 40 hand transplants around the world. In the United States, the other five were done over the past decade at the University of Louisville.

The lead transplant surgeon in Louisville, Dr. Warren Breidenbach, said yesterday that his team's experience has shown it possible to transplant functional hands to people who have lost theirs in traumatic accidents, and to keep their bodies from rejecting the new tissue.

In fact, Dr. Breidenbach and Dr. Lee said, the real challenge today in hand transplants is not the surgical techniques needed to attach the limbs, but minimizing the amount of anti-rejection medication that patients must take. Anti-rejection medications suppress the immune system, which can make a transplant patient vulnerable to infections or cancer.

UPMC's new "Pittsburgh protocol" starts by giving transplant patients a dose of a medication called Campath, which suppresses the patient's immune system, and then, within the first two weeks, infusing some of the donor's bone marrow into the recipient.

The hope is that when the patient's immune system rebounds from the Campath, it will recognize the new bone marrow cells as its own and thus won't attack the tissue of the transplanted hand.

In fact, Dr. Lee said yesterday, "I think there's clearly a chance of weaning Joshua off immunosuppressants altogether in the future."

Some bioethicists have questioned the risks of surgery and immunosuppression for transplants that are not life-saving, but Dr. Lee noted that it was "the concern about the risk-benefit balance that held us back for many years, because this is a quality-of-life transplant, and it is only now, when we are optimistic we can reduce the amount of medication the patient must take, that we decided to start this program."

UPMC has three more candidates waiting for hand transplants, two of whom would be double hand transplant recipients.

The key to the timing of any future transplants, he said, is finding donors that have the right tissue type, skin tone, gender and size to match the recipient.

As he waits for sensation and fine muscle control to develop in his new hand, Mr. Maloney is undergoing occupational therapy.

During the two years since his accident, he had begun using his left hand much more, said therapist Kim Zeske-Maguire, so now his brain has to be retrained to shift control back to the right hand.

For Mr. Maloney, there was no question about going forward with a hand transplant, because his experience with two types of prosthetics -- a mechanical hook prosthetic and a more lifelike one controlled by nerve impulses from his arm -- was frustrating. Or, as he put it, "I never used them because I found them to be a pain in the butt."

Dr. Lee said that is not atypical. Nearly 40 percent of all hand and arm amputees never use prosthetics, particularly men in their 20s and 30s.

"The prostheses become more of a burden than not," added hand surgeon Joseph Imbriglia, "and the reason is that they have no sensation."

Still, Dr. John Lantos, a bioethicist at the University of Chicago who did his pediatric training at the University of Pittsburgh, questions whether hand transplants are better than modern prosthetics, given the risks of surgery and lifelong medications.

What is needed, he said, is a controlled study comparing hand transplant recipients and prosthetics users on various tasks and quality of life measurements.

"You could look at such things as, can they pick up a penny, can they hold a pencil, can they eat with a spoon or play a piano -- you can imagine hundreds of things you could measure with the two groups where you could say in these domains transplant patients are doing as well, or worse or better. And then you'd have the possibility for truly informed procedures."

For Joshua Maloney, there was no other option that made sense to him.

Getting a hand transplant, he said, means "I get my life back. It's going to take some work, but I thought I would be limited after I got hurt, and now I won't be."