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The saliva of bloodsucking arthropods contains a large array of pharmacologically active compounds that assist hematophagy. Arthropod saliva is also responsible for causing uncomfortable allergic responses in its vertebrate hosts. In this article, we investigate whether the sand fly Phlebotomus papatasi, known to produce a strong delayed-type hypersensitivity (DTH) in humans, could benefit from, and possibly adaptively induce, this response in their vertebrate hosts. In this study, we show that flies fed on humans to completion nearly twice as fast in DTH sites as compared with normal skin sites. DTH sites had significantly larger blood flow as measured by the laser Doppler method. Sand flies feeding at sites in mouse ears that had a DTH response also fed faster than at normal sites. We conclude that in the case of P. papatasi, and possibly other arthropods such as fleas and bed bugs, the strong saliva-induced DTH response may reflect an adaptation of the fly to manipulate host immunity for the insect's own advantage.

Beryllium disease is caused by constant low-level exposure to the element beryllium. Lymphocytes, T cells and macrophages, cells of the immune system which fight off foreign substances in the body, overreact to beryllium and accumulate in the lung area. To determine whether the immune response, particularly that of the T cell, is specific or to beryllium or not, the blood of eight patients with beryllium disease and five healthy controls was examined. It was found that the increase of T cells in the lungs is moderated specifically by beryllium. The accumulated T cells therefore play a role in the development of the disease and indicate a hypersensitivity in susceptible individuals. Since not every person exposed to beryllium gets the disease, the response of T cells could be used to identify those individuals at risk.