The most important and most analysed IL-12-induced protein is Interferon-gamma (IFNG). In response to IL-12 normal T cells produce interferon-gamma (IFNG) (van de Vosse et al 2005). In PBMCs from subjects that lack the interleukin-12 receptor beta 2 subunit (IL12RB2) no interferon gamma is produced in response to IL-12, while in healthy subjects it is (de Jong et al 1998). To identify genes induced by IL-12, microarray analysis of over 33.000 genes was conducted using human PBMC enriched for CD3 + T cells after stimulation for 6 h with IL-12. Approximately 90 genes were differentially induced by IL-12 stimulation, of which IFNG was upregulated 24-fold (Watford et al 2008). Expression of IL-12 induced genes was also analysed by a microarray containing 6000 human genes, in differentiated Th1 cells. In these cells IL-12 induced a 53-fold upregulation of IFNG (Rogge et al 2000) Experiments using human cord blood CD4(+) T cells show 22 protein spots and 20 protein spots, upregulated and downregulated proteins respectively, following Interleukin-12 stimulation (Rosengren et.al, 2005).