Further studies on the inflammatory response induced by zinc wire implants in the central nervous system of rats

Implantation of zinc wires into the central nervous system of adult Lewis rats initiates an inflammatory reaction with a predominantly mononuclear cell profile. Extensive cuffs of small lymphocytes, mature plasma cells, macrophages, and histiocytes are found around the site of the wire implant and around adjacent blood vessels. The inflammatory response persists for at least 35 weeks but, with time , is gradually replaced by extensive fibrosis, collagen deposition, and proliferation of glial cells in the adjacent neuropil. The Lesion is not necrotic, nor is it characteristic of a foreign body granuloma, since neither giant cells nor organized epithelioid cells are found. No obvious clinical effect is observed. The fact that the implantation of zinc wire initiates an inflammatory response which resembles certain immune-mediated reactions is consistent with the reports of others that zinc affects immunological responses both in vivo and in vitro. Other metals (Be, Co, Mg, Pt, and Ni), implanted to control for the effect of zinc, initiated responses that were both distinct for the metal used and reproducible, and thus underscore the significance of studying the role of metals in both acute and chronic diseases.