Samples in both cDNA hybridisation experiments were paired as indicated with a dye-balanced arrangement (three cy3/cy5 & three cy5/cy3 hybridisations). Nv = "naïve" yearlings, worm naïve prior to challenge; Im = "immune" yearlings, previously infected by trickle infection prior to challenge (see Table 1). Common samples linked the sets of paired hybridisations (Expt 1: Nvd5 samples, Expt. 2: Nvd0 & Imd0 samples). An indirect comparison between the results from all three hybridisations gave the (Nvd2/Nvd0)/(Imd2/Imd0) gene list. aOne chip failed hybridisation QC in Expt 2 and so was removed from the analysis, along with chips linked to it.