Type 1 diabetes is a progressive disease. There is a genetic predisposition to type 1 diabetes, particularly conferred by alleles present within the major histocompatibility complex (HLA region) on the short arm of chromosome six. It is thought that in susceptible individuals, an environmental trigger initiates an immune response. Immune infiltration into pancreatic islets results in beta cell damage, impairment of beta cell function, and potential destruction of beta cells. One would expect that if type 1 diabetes is an immunologically mediated disease, then immune intervention should alter the natural history of the disease and potentially abrogate the clinical syndrome.
Intervention trials have been conducted at a number of stages of the disease process. Primary prevention trials have been conducted in individuals with a genetic predisposition who have not yet developed immunologic markers (“Pre-Stage 1”). Secondary prevention trials have been conducted in individuals with two or more diabetes-related autoantibodies, either during Stage 1 of type 1 diabetes (normal metabolic function) or Stage 2 of type 1 diabetes (abnormal metabolic function). Intervention trials, also called tertiary prevention trials, have been conducted in individuals with Stage 3 of type 1 diabetes (clinical hyperglycemia), usually shortly after clinical onset of disease.
This chapter provides brief summaries of the randomized controlled clinical trials that have been conducted and also mentions some non-randomized pilot studies. Unfortunately, none of the primary or secondary prevention trials have clearly arrested the disease process. Some tertiary intervention trials have demonstrated improved beta cell function, at least for some period of time, after which beta cell function has generally declined in parallel to that in the respective control group. This could be a consequence of most studies focusing on only a single immunologic mechanism; whereas, what may be required are studies that deal with multiple immunologic mechanisms, including attempting to improve regulatory immunity, while also addressing beta cell function by including interventions that improve beta cell health.