Lymphocytic inflammation produced by intracerebral implantation of zinc and other metals.

Sxteen pure metals were implanted as pellets of powder or as wires into the brains of rats. Al, Be, Cr, Fe, Pb, Sn, and W were relatively innocuous. Mg and Mn produced local necrosis. Bi, Cd, Co, Cu and Ni produced more severe local necrosis. Viable tissue adjacent to Co and Ni necrotic lesions had some perivascular lymphocytic infiltrates. Zn implants caused very little necrosis but adjacent areas had prominent perivascular lymphocytic cuffs. The infiltrates persisted for at least 4 weeks but disappeared as soon as the zinc was removed. Some compounds of zinc were also capable of inducing infiltrates. The perivascular infiltrates resembled the lesions of allergic encephalomyelitis, but there was no correlation between the ability of metal powders to induce lymphocytic infiltrates after intracerebral implantation and their adjuvancy after intraperitoneal injection with neural antigen.