Three young brothers owe their lives to the love of their older sister after she donated the bone marrow that saved them all.

Ciara MacMahon, seven, has undergone three operations for the sake of John, four and twins Rory and Edward, two.

Her bravery has been rewarded as Rory, the last of the three to be treated, has emerged from a sterile "bubble" to begin a new life.

All three boys suffer Severe Combined Immune Deficiency Syndrome (SCIDS), meaning they were born without an immune system.

It left them so susceptible to infections that even common illnesses like a cold or a kiss from their mother could kill them.

All three operations were carried out in a specialist unit at Newcastle General Hospital, where the boys are still having follow-up treatment.

Despite showing commendable courage Ciara, the only child in the family spared the condition, doesn't think of herself as a heroine.

She is just relieved that her bone marrow has saved Rory as it did Edward and John.

For the past 10 months parents Ben and Geraldine MacMahon watched as their sons took turns in a sterile bubble of air, an environment which became their home.

Ben, 36, said: "It is tough on Ciara because she has had to have general anaesthetics.

"The bone marrow was removed which involved drilling into the pelvis. She is very brave and we're proud of her.

"She knows too that she has helped all her brothers and she was happy to do the same for Rory."

Ben and Geraldine left their homes, jobs and family behind in County Limerick, Ireland, in March last year so the children could live in the special bubble environment.

Mr MacMahon said: "Our attitude was that it was going to be traumatic but it is better to do transplants when they are young than risk them getting huge problems as a result of infection."

The couple, even with the help of preventative antibiotics, must keep their home spotlessly clean and adhere to strict guidelines such as not keeping house plants, bread for more than a day and staying away from bacteria hotspots such as shopping centres.

"It will be a huge relief when we are through this as you can exist but you can't live like this forever," said Ben.

"I haven't been home in months and I look forward to a time when I can.

"We tend to shy away from people and it is not because we want to, it is just that they carry with them dangers we need to avoid."

The germ-free environment which has been so valuable for the boys is at the Bubble Appeal unit on Ward 23 of the hospital.

One of a handful in Europe, it protects children with SCIDS from the risk of infection which can be passed through touch or even clothing.

"The Irish Government have paid the medical bills but we have had to fund the trip and expenses for living here ourselves," said Ben.

"My job with the Met Office is being kept open for me but we've had to re- mortgage our house to raise funds."

He added: "John had some complications from the transplant - it is not uncommon to have difficulties with the liver after a bone marrow transplant - so he has been quite ill but is still doing okay.

"We are still taking precautions with Edward but he is also good.

"We didn't find out that John had the disease until after the twins were born but it did allow us to make sure Edward and Rory were given the preventative medicine as soon as possible."

It's also a comfort that Ciara, who is staying with an aunt back in Ireland, doesn't need to come to Newcastle because she already provided enough bone marrow for both of her twin brothers.

The 'bubble babies', as they are known at the unit, live inside a high-tech invisible bubble of totally clean air, 8ft by 8ft.

For Ben and Geraldine, like many parents in their position, one of the hardest things has been not being able to give their sons the physical comfort they have so desperately needed during their ordeal.

They were not able to kiss the boys while in the Bubble and before they were able to pick them up, they had to scrub their hands and dress in sterile gowns.

The family have endless praise for 24-hour care delivered by the 50-strong nursing team.

They hope the work of the unit is recognised and are encouraging donations in order that further, crucial research can be carried out.

"The Bubble staff are incredible," said Ben. "It's a six-week stint in hospital during the transplant process and then out to a half-way house.

"They are wonderfully supportive at every stage. On the ward itself there is a constant need for monitoring equipment.

"It is known which gene causes SCID but more research in to gene therapy is required."

Since the family moved to Newcastle they have been overwhelmed by the support they have received.

Ben said: "We received a £1,000 from Moonbeam Children's Cancer Charity to enable us to employ a nurse which was invaluable.

"We don't have any grandparents to fall back on as they died some time ago so it has been wonderful to receive the help."

Geraldine said: "it was lovely to have Rory out of the Scids unit, it is another milestone.

"But we are very aware that this is no the end of it, there is still some way to go for the boys.

"We are very proud of Ciara for what she had done I know she was very anxious about it and very frightened.

"But her concern all along has been for her younger brothers and that helped her cope."

Dr Andrew Gant of the SCIDS unit said: "I think it very unlikely that any of the boys would have survived childhood."