Molecular cloning, regulation of expression and characterization of porcine interleukin-12

Interleukin (IL)-12 is a heterodiineric cytokine consisting of 35 and 40 küa subunits. It is produced primarily by phagocytic cells in response to cellular interactions with bacteria or bacterial products. IL-12 is important in the regulation of both innate and antigen specific immunity through its stimulatory effects on natural killer cells and cytotoxic lymphocytes. Reverse transcriptase-polymerase chain reaction with primers derived from human sequence was used to clone the p35 and p40 subunits of porcine IL-12. Predicted amino acid sequences for both subunits are approximately 85% homologous to their human cognates but contain a 3 aa addition and a 4 aa deletion in p35 and p40 subunits, respectively. Both subunits of pIL-12 are constitutively expressed in a variety of porcine tissues. Highest levels of the p40 subunit were found in inguinal and mesenteric lymph nodes, Peyer's patches and thymus. The p35 subunit was also detectedin these tissues. Messenger RNA encoding the p40 subunit was rapidly induced in alveolar macrophages by stimulation with LPS or killed Stapkylococcus aureus. In contrast, p35 mRNA levels were not altered by these treatments. Thus, the heterodimeric subunits appear to be differentially regulated at the transcriptional level. Since p40 also self-αssociates to form inactive homodimers. differential expression may be a mechanism for regulating IL-12 activity.