Autoreactive T cells in mercury-induced autoimmune disease: in vitro demonstration

Mercuric chloride induces in Brown-Norway rats an autoimmune disease due to a T dependent polyclonal activation of B cells. Various autoantibodies and a striking increase in total serum IgE level are observed as consequences of this polyclonal activation. The aim of this study was to investigate the in vitro response of autologous syngeneic normal lymphocytes to lymphocytes exposed in vivo or in vitro to HgCL2. Helper/inducer T cells (W3/25 +) exposed to HgCl2 were found to stimulate normal T lymphocytes in the presence of normal Ia (+) cells. The proliferating T cells also had the helper/inducer phenotype. To demonstrate the potential relevance of this in vitro phenomenon to the autoimmune disease, HgCl2-pretreated T cells were injected into the footpads of normal syngeneic recipients. Draining popliteal lymph nodes contained a highly significant number of both surface IgE positive and IgE containing cells. These experiments demonstrate that HgCl2 induces autoreactive T cells and suggest that these cells may be responsible for the autoimmune disease.