I was just thinking that it's been a while since I wrote about the basic immune system problems that Fiona has. It would take a long time to read through all of the old posts, so I thought it would be good to write about it again. I also understand more that I did when I wrote the original post.
You are born with an immune system that can attack illnesses. It starts working right away. This is called innate immunity. Your immune system remembers the infections it has fought and can fight them off again, but in a better, faster way. This is called adaptive immunity. Adaptive immunity is the reason we get vaccinated. Our bodies remember the inactive or weakened viruses and can fight them off without getting sick.
B-cells protect your body from getting sick. They form antibodies that fight illnesses. There are three types of antibodies that B-cells form, IGA, IGG, and IGM. IGA protects your eyes, mouth, nose, lungs and intestines. IGG travels in your blood to fight germs. IGM protects your blood.
T-cells are another part of the immune system. They fight infections too. There are three types of T-cells, regulatory T-cells, helper T-cells, and killer T-cells. Regulatory T-cells tell your body when to stop fighting an infection. Helper T-cells tell killer T-cells where to fight, and they tell B-cells to make more antibodies. Killer T-cells kill germs.
Together T-cells and B-cells form your adaptive immunity. B-cells and T-cells are both called lymphocytes, and are produced in your bone marrow. Fiona's B-cells are defective. They don't produce as many antibodies as they should. Fiona also has low T-cell counts. Because of her low counts Fiona has very little innate, or adaptive immunity. If she is exposed to the illnesses we vaccinate for she would have very little response from her vaccinations, and her body would have a hard time fighting them off. The only fix for her problem is a bone marrow transplant.
The doctors don't understand why her immune system isn't working the way it should. They have tested for everything that could cause her low counts and everything comes back normal. We are still waiting to see if her genetic tests show any mutations.