A role for B cell-activating factor of the TNF family in chemically induced autoimmunity.

After exposure to subtoxic doses of heavy metals such as mercury, H-2s mice develop an autoimmune syndrome consisting of the rapid production of IgG autoantibodies that are highly specific for nucleolar autoantigens and a polyclonal increase in serum IgG1 and IgE. In this study, we observe that HgCl2 administration in susceptible mice results in the elevated production of B cell-activating factor of the TNF family ((BAFF) also known as BLyS, TALL-1, zTNF-4, THANK, and TNSF13B), a B cell growth factor belonging to the TNF family. A transmembrane activator and calcium-modulating and cyclophilin ligand interactor (TACI)-Ig fusion protein (which neutralizes both BAFF and a proliferation-inducing ligand (APRIL), another TNF family member) inhibited Hg-induced autoantibody or serum IgE production. These results are discussed in the context of the inhibitory effect of TACI-Ig on B cell maturation at the transitional stage.