Recently, we found that parenteral arginine supplementation at a dose of 2 to 6% of total calories may decrease circulating levels of interleukin (IL)-2 and nitrite/nitrate (NOx), the indirect biomarkers of NO, and may modulate the immunocytic subpopulation and cytokine production in peripheral blood leukocytes and splenocytes in a U-shaped dose-dependent manner in rats with sub-acute peritonitis [5], [6]. Here, IL2 is linked to peritonitis.