C3 and infection: Several of the genes observed to be induced in this study have previously been described to be induced by infection including those encoding IL-6 and IL-6 signal transducer (IL6ST), alveolar macrophage-derived chemotactic factor-I (AMCF-I) which is the porcine homologue of human IL-8 [21], IL-8 receptor beta (IL8RB), chemokine-like factor super family 8 (CKLFSF8), IL-11 receptor alpha (IL11RA), suppressor of cytokine signalling 3 (SOCS3), cytokine inducible SH2-containing protein (CISH) transcript variant 2 and complement component 3 (C3).