Answer the following question given this paragraph: 

One example is type 1 diabetes . In this disease, the immune system attacks cells of the pancreas. Other examples are multiple sclerosis and rheumatoid arthritis. In multiple sclerosis , the immune system attacks nerve cells. This causes weakness and pain. In rheumatoid arthritis , the immune system attacks the cells of joints. This causes joint damage and pain.


Q: What system is involved in diseases that include type 1 diabetes, rheumatoid arthritis and multiple sclerosis?


A:
immune system