All of us have a very focused field of investigation, so I won't speak in general terms.
One commonality in many diseases is inflammation. Arthritis is an inflammatory disease. Some neurological conditions are inflammatory diseases. We're discovering that even infectious diseases involve inflammation. If we can understand how the immune system works, how the inflammation process works, and exactly how particular drugs interfere with that inflammatory process, it would be just one example of how understanding basic processes of inflammation may have impacts on many different diseases.