Adjuvant activity of muramyldipeptide in a guinea pig model of contact allergy to chromium.

New chemical agents encountered increasingly in the human environment underline the urgent need for a routine testing of their sensitizing potential for man and the development of a suitable experimental model appears to be essential for a reliable assessment of this potential. In our present experiment we studied a guinea pig model of contact hypersensitivity to chromium using as immunoadjuvants Freund's complete adjuvant (FCA) and Freund's incomplete adjuvant (FIA) emulsified with muramyldipeptide. The study showed that the use of adjuvants was essential for inducing the state of hypersensitivity in experimental animals. It was also demonstrated that muramyldipeptide was not only a fully potent substitute for FCA, but was even superior to it in all the parameters tested. The optimal time interval for demonstrating the induced hypersensitivity to chromium was the third week after the onset of sensitization. This animal model appears to be well suited for the experimental testing of contact allergen potentials.