Human and murine PMNs differ in the regulation of arginase I expression. (A) Constitutively expressed arginase I in human PMNs is not further induced by TH2 cytokines. Human PMNs were stimulated with the indicated cytokines for 14 hours. Arginase I protein expression was analyzed by immunoblotting. (B) Induction of arginase I protein in murine PMNs by TH2 stimulation. Bone marrow-derived murine PMNs were stimulated with the indicated cytokines. After 14 hours, the cells were harvested and analyzed by immunoblotting. In panels A and B the results of parallel determinations of arginase activities (in mU/mg protein) in aliquots of the same cell lysates are noted above the respective lanes of the arginase blots. To control for equal protein loading, Western blots for ERK1/2 were done in parallel. Results shown are representative of 4 independent experiments.
