Immunosuppression by the disease modifying antirheumatic drug bucillamine: inhibition of human T lymphocyte function by bucillamine and its metabolites.

Objective. Bucillamine: N-(2-mercapto-2-methyl-propanoyl)-L-cysteine has recently been suggested to be effective in the treatment of rheumatoid arthritis (RA). The molecular structure of this compound is similar to that of D-penicillamine, except that bucillamine has 2 free sulfhydryl groups in its structure whereas D-penicillamine has only one. The goal of our studies was to determine whether bucillamine exerted immunosuppressive effects in vitro. Methods. The effect of bucillamine and its metabolites on mitogen induced proliferation and IL-2 production by human T cells was examined. Results. Bucillamine, and its metabolites SA 679, and SA 981 inhibited mitogen induced T cell responses