Chronic cell-mediated immune reactions to metals.

Cell mediated immune reactions may underly toxic reactions to certain metals, particularly Cr, Ni, Zr, Be, and Hg. Metal conjugated to a carrier protein forms the immunogen, but how the metal acts as a hapten is poorly understood. The possibility that the metal changes the antigenicity of the protein by changing its configuration is discussed and could explain cross reactions between Zr and Cr. Most reactions are contact sensitivity reaction, but granulomas may also develop to Be and Zr. These are epithelioid cell lesions associated with fibroblast proliferation and increased collagen synthesis. Sensitization of guinea pigs to Be and Hg is possible by epicutaneous contact. Cr, Ni, and Zr sensitivity need Freund's adjuvant and frequent intradermal injections. Three initial protocols have been compared and their efficacy for each metal assessed. Specific unresponsiveness for Cr and Ni can be induced by intratracheal installation prior to attempted sensitization. After sensitivity has developed, unresponsiveness to Cr can be induced by intravenous injection of the metal together with an epicutaneous application given within 24 hours. Flare up of old Cr reaction sites can also be induced by intravenous injection of the metal. The reaction lasts for 48 hours, is associated with increased vascular permeability and subepidermal infiltration with basophil leucocytes.