Participants will receive injections of interferon gamma under the skin 3 times a week for 3 months. Adult patients will be taught how to give their own injections (similar to insulin injections for diabetes) and parents will be taught how to administer the shots to their child. Blood samples, usually be between 30 to 90 milliliters (2 to 6 tablespoons), will be drawn just before starting medication and again 1 day, 1 week, 1 month, 3 months and 4 months after therapy begins. At these same time intervals, patients will provide a salt-water mouth rinse specimen, which will be tested for changes in the number of white blood cells during interferon gamma treatment.