PORCINE CYTOKINE RESPONSES TO PAMP-STRUCTURES IN VITRO.: KINETICS COMPARING EXPRESSION ON MRNA AND PROTEIN LEVEL

Pathogen-associated molecular patterns (PAMPs) are conserved microbial structures recognized by pattern-recognition receptors (PRRs) of the innate immune system. Binding of PAMPs by certain PRRs on dendritic cells induces these to express costimulatory molecules and cytokines, enabling an inductive antigen-presentation.

Different PAMPs will activate different signalling pathways, resulting in specific cytokine signatures, which will influence the orientation of a developing immune response. In the pig, the range of antibodies available for cytokine-detection is limited, and so cytokines are often monitored at mRNA-level only.

However, mRNA levels do not always correlate with corresponding protein levels, and translational regulation is abundant, e.g. exerted by microRNAs through inhibition of mRNA-translation. Here, the kinetics and magnitude of induction of cytokines (IFN-α, IL-12 p40, IL-1β, TNF-α, IL-6 and IL-10) by PAMP-structures (oligonucleotides, single-stranded RNA, peptidoglycan, lipopeptides and lipopolysaccharide) were investigated in porcine PBMCs comparing expression at mRNA (quantitative real-time PCR, qPCR) and protein level (ELISA).

Overall, the two levels correlated well, with the protein response in most cases being slower than the mRNA response, as expected. Different PAMPs induced different cytokines with varying kinetics of induction. In some cases qPCR appeared more sensitive than ELISA, but to what degree this could be explained by translational inhibition or by different detection-sensitivities of the two techniques is not known at this point.