A prostitute goes to the hospital to visit a colleague...

A prostitute goes to the hospital to visit a colleague who is about to have a heart transplant. She's worried about the friend so she asks the doctor: Girlfriend: I'm worried about my friend doc, what if her body rejects the organ? Doctor: Well she's 36 years old and healthy. How long has she been in business? Girlfriend: She's been working since she was 19 years old but what does that have to do with anything? Doctor: Well she's been working 17 years and hasn't rejected an organ yet!