Figure 3.

Interplay between host and parasite arginase influence disease outcome. The macrophage, phagolysosome, and intracellular parasite are shown. Indicated in yellow boxes are the opposing Th1 and Th2 responses with associated cytokine production. White boxes denote macrophage polarization towards an M1 or M2 phenotype with resulting parasite killing or proliferation. The conversion of arginine to nitric oxide or polyamines in the macrophage is shown with solid arrows, as is the conversion of arginine to polyamines and trypanothione in the intracellular parasite. Uptake of arginine, ornithine, or polyamines is shown in hashed arrows. The essential uptake of arginine by parasites is indicated; the question marks denote that ornithine and polyamine salvage has not been directly demonstrated in intracellular parasites.