Four fragments of the bovine IL-12 receptor beta2 were sequenced following generation by reverse transcriptase polymerase chain reaction (RT-PCR) amplification of RNA from mitogen-activated bovine peripheral blood mononuclear cells (PBMC). Primers were based on sequences within regions of the human IL-12Rbeta2 gene that displayed high levels of similarity with the mouse IL-12Rbeta2 gene sequence. The amplified bovine IL-12Rbeta2 fragments had 82-87% similarity at the nucleotide level with human IL-12Rbeta2 and 70-88% similarity at the predicted amino acid level. Bovine IL-12Rbeta2 gene expression was induced following culture of PBMC with Concanavalin A (Con A), with immobilized monoclonal antibody to CD3 or with human recombinant IL-12 p70 and correlated with interferon-gamma (IFN-gamma) production. Expression of bovine IL-12Rbeta2 by PBMC was detected by 2h of culture with Con A and sustained for at least 5 days when cultured with rHuIL-12. Expression, however, did not require cellular proliferation since IL-12 did not induce proliferation, although both Con A and anti-CD3 monoclonal antibody did do so. Addition of rHuIL-10 inhibited IFN-gamma production without abrogating bovine IL-12Rbeta2 gene expression.