Correct. Let's zoom in a bit: The main target of the immune system in Type 1 diabetes are the beta cells in our pancreas. These Beta cells are responsible for making INSULIN which lowers the amount of sugar in our blood. When damaged, they no longer produce insulin, and sugar becomes stuck in our blood!
BONUS: Our pancreas also has alpha cells which are responsible for making glucagon. Glucagon does the opposite of insulin and actually increases the amount of sugar in our blood.
When we go a long time without eating and our blood sugar starts to drop, our body should make glucagon to help fuel us. More on Glucagon upcoming.