Antigen presentation of detergent-free glutamate decarboxylase (GAD65) is affected by human serum albumin as carrier protein

Was the appearance of surfactants in air breathing vertebrates ultimately the cause of decompression sickness and autoimmune disease?

All air breathing vertebrates are endowed with pulmonary surfactants, surface-active lipoprotein complexes formed by type II alveolar cells. Surfactants are deposited in clearly defined areas on the luminal aspect of blood vessels, producing hydrophobic spots. Gas nanobubbles measuring 5-100nm form spontaneously on the smooth hydrophobic spot from dissolved gas. Bubbles nucleate and grow at these spots after decompression from high pressure. Proteins with hydrophobic regions circulating in the blood will adhere to the gas phase-plasma interface. Deformation of their secondary and tertiary configuration will present them as foreign molecules or autoantigens. Components of the intact protein which are also present in a deformed protein may be recognized as foreign too. This process is proposed as the trigger for autoimmune diseases. The presence of autoimmune disease in air breathing vertebrates, increased autoimmunity and the elevated risk of decompression sickness with age, as well as variable sensitivity to both diseases, can be matched with the appearance of surfactant spots. Eliminating these spots may provide protection against both diseases.

Immune therapy in type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is an autoimmune disorder directed against the β cells of the pancreatic islets. The genetic risk of the disease is linked to HLA-DQ risk alleles and unknown environmental triggers. In most countries, only 10-15% of children or young adults newly diagnosed with T1DM have a first-degree relative with the disease. Autoantibodies against insulin, GAD65, IA-2 or the ZnT8 transporter mark islet autoimmunity. These islet autoantibodies may already have developed in children of 1-3 years of age. Immune therapy in T1DM is approached at three different stages. Primary prevention is treatment of individuals at increased genetic risk. For example, one trial is testing if hydrolyzed casein milk formula reduces T1DM incidence in genetically predisposed infants. Secondary prevention is targeted at individuals with persistent islet autoantibodies. Ongoing trials involve nonautoantigen-specific therapies, such as Bacillus Calmette-Guérin vaccine or anti-CD3 monoclonal antibodies, or autoantigen-specific therapies, including oral and nasal insulin or alum-formulated recombinant human GAD65. Trial interventions at onset of T1DM have also included nonautoantigen-specific approaches, and autoantigen-specific therapies, such as proinsulin peptides. Although long-term preservation of β-cell function has been difficult to achieve in many studies, considerable progress is being made through controlled clinical trials and animal investigations towards uncovering mechanisms of β-cell destruction. Novel therapies that prevent islet autoimmunity or halt progressive β-cell destruction are needed.

Vaccination against type 1 diabetes

The clinical onset of type 1 diabetes or autoimmune diabetes occurs after a prodrome of islet autoimmunity. The warning signals for the ensuing loss of pancreatic islet beta cells are autoantibodies against insulin, GAD65, IA-2 and ZnT8, alone or in combinations. Autoantibodies against, for example, insulin alone have only a minor risk of type 1 diabetes. However, progression to clinical onset is increased by the induction of multiple islet autoantibodies. At the time of clinical onset, insulitis may be manifest, which seems to reduce the efficacy of immunosuppression. Autoantigen-specific immunotherapy with alum-formulated GAD65 (Diamyd(®)) shows promise to reduce the loss of beta-cell function after the clinical onset of type 1 diabetes. The mechanisms are unclear but may involve the induction of T regulatory cells, which may suppress islet autoantigen reactivity. Past and ongoing clinical trials have been safe. Future clinical trials, perhaps as combination autoantigen-specific immunotherapy, may increase the efficacy in preventing the clinical onset in subjects with islet autoantibodies or preserve residual beta-cell function in patients newly diagnosed with type 1 diabetes.