The effects of antisense (AS) oligodeoxynucleotides (ODNs) on interleukin 10 (IL-10) and interferon gamma (IFN-[gamma]) production induced by lipopolysaccharide (LPS) and concanavalin A (Con A) were investigated using swine blood mononuclear cells. Antisense phosphorothioate ODNs (PS-ODNs) corresponding to a sequence in the neighborhood of the AUG initiation codon of swine IL-10 or IFN-[gamma] mRNA, which has more than 50% G:C content in its antisense sequence, inhibited production of IL-10 and IFN-[gamma] proteins and mRNAs. Controls, scrambled and sense ODNs had no such effect. Cytokine-specific competitive enzyme immunosorbant assay (c-EIA) analysis using antiswine IL-10 or IFN-[gamma] revealed that AS ODNs specifically inhibited IL-10 and IFN-[gamma] protein production by more than 95%. In addition, the results of real time reverse transcription polymerase chain reaction (RT-PCR) revealed that the AS effect originated from a specific reduction of the targeted IL-10 and IFN-[gamma] mRNA levels by hybridization with the AS ODNs. Furthermore, none of these ODNs inhibited the induction of [beta]2-microglobulin mRNA expression in blood mononuclear cells stimulated by LPS or Con A. These findings demonstrate that, in each case, the effect of AS ODNs was specific for its target IL-10 and IFN-[gamma] mRNAs.