WESTWOOD (CBSLA.com) — About 100 UCLA kidney transplant recipients and their donors united Monday for a holiday celebration.

CBS2’s Lisa Sigell reports that the gathering at Ronald Reagan UCLA Medical Center was to recognize living donor transplant “chains,” which begins when a man or woman donates a kidney. The organ is then transplanted into a recipient who had a willing donor, but was not a match. The incompatible donor then gives a kidney to another patient.

READ MORE: Long Beach Unified Pauses COVID Testing For Students

The UCLA Medical Center has participated in more “chains” than any other transplant center in the world.

Dr. Jeffrey Veale, the director of the UCLA Kidney Exchange Program, was overjoyed about the special milestone.

“I didn’t know when I started to do transplants … it was usually spouses who give a kidney to a spouse or a brother gives a kidney to a sister. That kind of thing. I wasn’t expecting that there were total strangers that give kidneys to strangers,” he said.

READ MORE: Mother, Daughter Face Murder Charges After Illegal Butt Implant Procedure Kills Aspiring Social Media Star Karissa Rajpaul

Sheila Whitney, of Compton, said she received a kidney from a donor in Michigan.

“When I received the kidney, it was like, a miracle,” she said.

Whitney’s son, Reggie, then donated his kidney to man. That man’s wife gave her kidney to another woman.

Donor Greg Thompson was emotional when he discussed how the “chain” affected his life.

MORE NEWS: Fall Quarter Begins At UCLA, Bringing Students Back to Campus For First Time In More Than 18 Months

“We have three [granddaughters]. That my wife would not be sharing if it wasn’t for this program,” he said.