GAPDH and infection: However, infected BHK cells did not express IL-4 mRNA (by real-time RT-PCR the CT value for GAPDH was 22.9±0.09 and the CT value for IL-4 was below the threshold limit of detection), and expressed very low basal levels of IL-13 that did not increase with infection (after correction for GAPDH expression the fold-increase relative to the BHK calibrator was 1.14 ± 0.16 for uninfected cells and 0.98±0.2 for infected cells; p = 0.16), suggesting that the parasite-induced arg1 expression was independent of type 2 cytokine synthesis.