A Closer Look At The Mind Of An Altruistic Kidney Donor

BOSTON (CBS) -- What does it take to give the gift of life to a complete stranger? Researchers in Washington, D.C. studying the brains of altruistic kidney donors found they all have something in common.

As a mother, firefighter and paramedic, putting others first is a way of life for Jo Kummerle. It wasn't a difficult choice when she decided to donate one of her kidneys to a total stranger.

"I guess I just keep thinking why not?" said Kummerle. "Why would you not? I've always been a helper, I always love people. Why wouldn't I?"

Kummerle is one of just a few hundred people every year who become altruistic kidney donors.

Professor Abigail Marsh at Georgetown University is studying the brains of those donors, including Kummerle, to understand why some people are simply more altruistic than others. She spoke to CBS's Kenneth Craig and the images are telling.

"They seem to have just a little extra matter, a little extra material in this region of the brain that we know is really important to producing an empathic response," said Marsh. "There is a structure in the brain called the amygdala and people that are psychopathic have smaller than average, and in altruistic kidney donors, it's larger than average by about eight percent."

Kummerle, who lives in Washington State, donated her kidney to Tressa Dombroski in New Jersey. Dombroski is a married, mother of two with an autoimmune disorder who needed a second kidney transplant after her first started to fail.

"You go through an illness, a serious illness where your organs are failing, you don't ever take that for granted again," said Dombroski. "It gives you a whole new perspective on life, really."

Dombroski was able to thank Kummerle in person when they met for the first time three years ago in Washington. It was an instant friendship.

Nearly 100,000 people U.S. are currently waiting for a kidney transplant.