MELISA-an in vitro tool for the study of metal allergy.

The sensitizing properties of metals widely used in medical and dental care have been studied with the help of an optimized lymphocyte proliferative assay, MELISA. MELISA (memory lymphocyte immuno-stimulation assay) was originally developed for the screening of allergenic epitopes of drugs and other chemicals of low molecular weight, but has recently been adapted for the study of metal-induced sensitization. The patients studied suffered from various oral mucosal problems which were suspected to be caused by the release of metal ions from dental restorations. They were also troubled by chronic fatigue persisting over many years. One patient was also occupationally exposed to metals while working in a dental practice. Healthy subjects without any discomfort due to metal devices served as controls. In addition to metals used in dentistry, lymphocyte responses to organic mercurials used widely as preservatives in vaccines, eye/nose drops and contact lense fluids were studied. The results indicated that mercurials, as well as other metals such as gold or palladium, induce strong lymphocyte proliferative responses in patients with oral or systemic symptoms, but not in similarly exposed unaffected subjects. The results of MELISA performed with a pair of identical twins with chronic fatigue syndrome (CFS) indicated that metal-specific responses may be dependent on the genetics of the patient. Thus, many metals that are today accepted for use in medicine and dentistry carry a definite sensitizing risk for certain genetically predisposed individuals. Therefore, the use of these metals should be limited in the future.