Seemingly unique genes within the top 30 gene set of the incipient TB subgroup, such as CCL2, HESX1, PCGF2, LCN8, and SIGLEC1, were only elevated to a very low level against controls in the full set of differentially expressed genes, potentially suggesting that they may come up early in the immune response to M. tuberculosis, although they were also expressed at a low level in clinical TB (Data S1; full incipient TB, full clinical TB versus control tabs). This evidence concerns the gene PCGF2 and tuberculosis.