Evidence that scabies mites (Acari: Sarcoptidae) influence production of interleukin-10 and the function of T-regulatory cells (Tr1) in humans.

We performed experiments to determine whether an extract of Sarcoptes scabiei (De Geer) influenced cytokine expression by human T-lymphocytes. Peripheral blood mononuclear cells from five sensitized donors and four donors without sensitization to scabies mites were challenged with a T-cell mitogen alone, with scabies extract (SS) alone, or with mitogen and SS together. Supernatants were analyzed for the cytokines interferon-gamma (IFNgamma), interleukin (IL)-2, IL-4, and IL-10. No IL-2 or IL-4 was produced in response to scabies extract. Cells from both naive and sensitized donors produced large amounts of IFNgamma and IL-10. The lack of IL-4 but high levels of IL-10 suggests that IL-10 was likely secreted by type 1 T-regulatory cells, which were activated by something in the scabies extract. IL-10 has anti-inflammatory and immune-suppressive effects. It may play a key role in depressing the inflammatory and immune responses in humans so that clinical symptoms are not seen until 4-6 wk after a person becomes infested with scabies mites.