Opposite changes in serum soluble CD8 in patients at the active stages of Graves' and Hashimoto's diseases.

Serum concentrations of soluble CD8 (sCD8) were examined by enzyme immunoassay in 154 patients with autoimmune thyroid diseases and 46 healthy controls. The numbers of peripheral CD8+ cells were also examined in the same subjects by flow cytometry. The serum concentrations of sCD8 were increased in patients with stimulative thyrotoxicosis caused by active Graves' disease, and decreased in patients with transient destructive thyrotoxicosis caused by the aggravation of Hashimoto's disease, and normal in euthyroid and hypothyroid patients with Graves' or Hashimoto's disease. The ratios of serum sCD8 levels to the numbers of CD8+ cells were increased in thyrotoxic patients with active Graves' disease, but not with active Hashimoto's disease, suggesting an increase in sCD8 production by CD8+ cells in active Graves' disease. The serum concentrations of sCD8 were correlated with the serum levels of thyrotropin receptor antibody (TRAb) and thyroid hormones in Graves' disease. These data indicate that serum sCD8 proteins change in opposite directions in the active stages of Graves' and Hashimoto's diseases, and may represent the disease activities.