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For a sister and brother, Danielle and Deren Rehr-Davis are more compatible than most.

"We're best friends," said 15-year-old Danielle of her almost-13-year-old sibling. "We hardly ever fight. We hang out together. Play together. I tell him I love him and he tells me he loves me."

This pair's compatibility isn't just skin deep. It goes right to the bone marrow — which is a good thing because last February, Deren was able to save his sister's life by donating marrow to her.

"If it wasn't for [Deren] I wouldn't have lived," Danielle, a first-year student at Piedmont High School and a congregant at Oakland's Conservative Temple Beth Abraham, explained. She was diagnosed with leukemia just over a year ago.

She was lucky: Her brother was a match. Although the odds, at 1 in 4, were pretty good, if Deren had not been a match, things could have turned out quite differently. The odds of a Caucasian finding a match in the general population are 1 in 20,000, according to Ann Bruster of the Blood Centers of the Pacific. And since Danielle is Jewish, her odds, as with any minority, are even lower.

Although she's not entirely out of the woods, every day Danielle gets better and her illness drifts further into the past. She's back at school, playing soccer and has her brother's blood flowing in her veins.

"I have boy's blood," declared Danielle, who, unlike most females, now has both X and Y chromosomes. Her blood type also has converted from A-positive to A-negative.

Danielle and her family were lucky in other ways, too. Throughout the long ordeal, Beth Abraham members organized Shabbat baskets to send to the hospital every Friday, sent meals to the house and the hospital during the week. In addition, they helped care for Deren, arranging to bring him to and from Hebrew school and other activities, according to Howard Davis, Danielle and Deren's father.

"It was overwhelming, the support," said Davis, who has been affiliated with the synagogue for 50 years. The synagogue's former rabbi, Mark Diamond, visited the hospital frequently, bringing an electric menorah for Chanukah and electric candlesticks for Shabbat, as fire was prohibited. Hospital doctors who were temple members checked in on the family. And other members "just came all out from everywhere — either calling and letting us know they were there for us," or providing cards and assistance. "Of course, we're very grateful."

This saga began in November 1999, when Danielle was first diagnosed with an aggressive form of the disease. It was one of those things that came out of nowhere. Her main symptom was fatigue, which at first she and her parents attributed to a cold. But when Danielle wasn't able to walk up the block, her mother made a doctor's appointment for the next afternoon.

"The doctor sent us directly to Children's Hospital [Oakland] for testing," said Danielle's mother, Elaine Rehr. "We were clueless. Even when they said leukemia, they were more visibly upset than we were. I didn't even know what it meant at the moment."

But reality set in quickly. Danielle was immediately taken to surgery, where a permanent IV was put in, and then she was sent to the intensive care unit, where she received blood transfusions all night Rehr said she doesn't think she's "ever cried as much as I did that entire night." Two days later, Danielle started chemotherapy and thus began a course of treatment that is just now coming to an end. The first time Danielle left the hospital was in early February when she was allowed to go home for 10 days before going to Stanford Hospital for the bone marrow transplant.

The harvesting and transplant happened on Feb.15, the day before Deren' s 12th birthday.

"The doctor came in with a big bag of bone marrow," said Danielle, who described it as looking like "blood with sand in the bottom." The marrow is transplanted through intravenous transfusion, a procedure that takes several hours. While it was going on, Danielle's brother, parents, nurses, doctors and Diamond were there. "It was like watching a miracle happen. I felt really special. [Deren] felt really special."

Because Deren's blood as well as his marrow were compatible, Danielle was able to receive an extra boost from her brother. It was something that left him depleted, but according to their mother, given the benefit to Danielle, it was worth it.

But for several weeks afterward it was still a wait-and-see situation.

"I watched her degenerate daily," said Rehr, who described her daughter at the time as a "dead woman walking." To prepare Danielle for the transplant, all of her bone marrow cells had to be killed off. Until the engraftment occurs — when her body accepts the new bone marrow — she had no blood and no marrow. During the first six weeks following a transplant, the mortality rate is 15 percent. "It's a horror beyond anything imaginable. Every day is worse than the day before. Death seems one minute away every minute."

For weeks, Danielle was in constant, acute pain. She lost all the hair on her body and sloughed off skin, including that in her mouth. Danielle remembers the top of her tongue coming off. She was too weak to get out of bed, even with assistance. She couldn't ingest any food orally and all nourishment came through a tube.

But in spite of what she was going through, Danielle's attitude was positive and she remembers repeating to herself, "I'll make it through. I'll be OK. I'm going to live."

Fortunately Danielle has forgotten a lot of what went on during this time. But she does remember the day things turned around and she suddenly started to feel better. But that's relative. Feeling better meant she could get out of bed with the assistance of four nurses and her mother.

"The things I taught I had to live," said Rehr, who teaches psychology at Diablo Valley College. "Most of the time, you're responsible for your life but sometimes you're a victim. But you have control over how you handle it."

Rehr took a leave of absence from her job and her husband, Davis, worked minimally. Danielle was never alone during all the months she was in the hospital and family friends helped give Deren the attention he needed when his parents couldn't.

"I had a lot of support from family, friends and the temple," said Danielle, adding that when it was allowed, friends came to see her. "That helped me tremendously."

Beth Abraham hosted a bone marrow registry and blood donation drive last January and will host another on Sunday. Danielle will be there as living proof of what mitzvah means.

Last year's drive was a tremendous success. According to Kimberly Roberts of the American Red Cross about 150 people were added to the bone marrow registry and 118 pints of blood were collected — about twice what the usual blood drive produces.

Danielle isn't the same person she was a year ago — inside or out. Her father says she's much more compassionate than she used to be. Danielle says she "cherishes life 1,000 times more. Every day I thank God he gave me a second chance."