Gold is a T cell polyclonal activator in BN and LEW rats but favors IL‐4 expression only in autoimmune prone BN rats

Gold salts are beneficial in the treatment of rheumatoid arthritis but may induce immune‐mediated disorders in predisposed patients. Gold salts induce Th2‐dependent autoimmunity in Brown‐Norway (BN) rats but not in Lewis (LEW) rats. The aim of this study was to define molecular targets of gold salts and to approach why LEW rats are resistant. Gold salts act on early steps of transductionin T cells from BN and LEW rats since they trigger tyrosine phosphorylation of numerous proteins including p56lck and a calcium signal which results in IL‐4 and IFN‐γ expression by BN and LEW T cells. However, the IL‐4 response was favored in BN spleen cells in vitro and in vivo. IFN‐γ, produced in part by CD8+ cells, contributes to the resistance of LEW rats since gold salt‐injected LEW rats receiving anti‐CD8 or anti‐IFN‐γ mAb displayed the parameters characteristics of gold salt‐induced Th2 autoimmunity although to a lesser extent than in BN rats. Gold salts transduce a signal in BN and LEW spleen cells resulting in IL‐4 and IFN‐γ gene transcription with a preferential IL‐4 response in BN rats, a Th2‐prone strain, while IFN‐γ contributes to the resistance of LEW rats.