There are several type of islet cells including alpha cells and beta cells.Insulin is produced by beta
cells. On increase of sugar in the blood, these cells manufacture insulin and then release into the
blood stream.The roll of these cell is to monitor levels of blood sugar. In people with Type-1
diabetes, beta cells are attacked by the immune system and are destroyed slowly. What exactly
causes the immune system to get affected is still based on a number of theories. The unfortunate
part is that, though this slow destruction takes place over a number of years (5-7), the symptoms
of diabetes mellitus do not surface until about 80% of these beta cells are destroyed. Eventually,
insulin production comes to a halt as no beta cells remain.