Evaluation of cellular and humoral autoimmunity before the development of type 1 diabetes in a patient with idiopathic CD4 lymphocytopenia

A 64-year-old woman developed type 1 diabetes 23 years after the diagnosis of idiopathic CD4 lymphocytopenia. To investigate the etiological interaction between idiopathic CD4 lymphocytopenia and type 1 diabetes, we carried out a longitudinal analysis related to islet-specific autoimmunity. Anti-glutamic acid decarboxylase antibody had been already weakly positive for at least 16 years and started rising at 6 months before the onset of type 1 diabetes. The seroconversion of anti-insulinoma-associated antigen-2 antibody and insulin autoantibody occurred at the time of onset. The ratio of CD8/CD4 had been gradually increasing for 8 years before type 1 diabetes onset. Notably, islet-specific glucose-6-phosphatase catalytic subunit-related protein-reactive CD8⁺ T cells were detected at type 1 diabetes onset, and the frequency was higher than that in 15 non-diabetic controls (6.75% vs 0.49 ± 0.78%, mean ± SD). The present type 1 diabetes patient, presented with idiopathic CD4 lymphocytopenia and showed an elevated number of CD8⁺ T cells, including the islet antigen-specific CD8⁺ T cells that might contribute to autoimmune destruction of pancreatic β-cells.