“…A. pleuropneumoniae has a multifactorial pathogenicity, involving different secreted and non-secreted virulence factors, including lipopolysaccharide (LPS), cytotoxins (Apx toxins), hemolysin, proteases, host and environmental factors (Haesebrouck et al, 1997;Huang et al, 1998;Chiers et al, 2010). Reports on systemic cytokine production following experimental infections with A. pleuropneumoniae in pigs are not as straightforward (Fossum et al, 1998;Huang et al, 1999;Balaji et al, 2002;Myers et al, 2004). Only IL-6 has been consistently detected in the majority of infected pigs and has consequently been put forward as a valuable marker for bacterial infections (Fossum et al, 1998).…”