Whenever you’re exposed to something foreign, you develop antibodies to that. So, if it’s a blood transfusion, you develop antibodies to the blood transfusion; pregnancies can give you antibodies – these are all called sensitisation events. And having a transplant is one example, where a host of different antigens, you’re exposed to them, and you develop antibodies to those antigens. So these are the stimuli that trigger your immune system, and one thing we know for sure is your immune system has a memory that remembers anything it’s been exposed to in the past. And when it sees the same antigen coming back, it calls upon its army of immune cells to basically bash up whatever’s coming, assuming that it’s trying to invade your body. So it’s a natural response and as a result we have to give immunosuppression to damp down that immune response so that they accept the organ without overwhelming the particular person such that they’re overexposed to infections, and that balance can be quite difficult to achieve.