Arginase 1 expression is increased in response to parasite implant in C57BL/6 but not IL-4 -/- mice. Real-time PCR analysis of arginase 1 expression by total cells (A) or F4/80 purified macrophages (B) obtained from peritoneal lavages of implanted or control mice. For the purified NeMφ, each cDNA sample was obtained from individual mice. For the purified control macrophages, the cDNA samples represent pooled macrophages from 5 mice. Expression levels were measured as a percentage of β-Actin expression. Error bars represent one SD from the mean of each analysis.