at the age of 80 you must remember that this was about 25 years age so memory can be hazy. the doctor was referring to my lungs at this period of time. i am not a doctor nor an expert but i was told that in-between everything there is something. hence the interstitial. i must look this up again on google or wherever. i could be so wrong. must look this up again. my proposition is that if the interstitial is everywhere, then it can affect everything within the body especially i if there is an infection in the interstitial. this is just an old age mind reflecting on life. should have gone further in school studying in this field. just a dream of another generation.