Immunohistochemistry controls, positive (exposed to specific antibody) and negative (not exposed to specific antibody) from trophozoites, macrophages and neutrophils. Hamster liver rich in trophozoites (arrowheads) in negative (a) and positive (b) controls for Immunohistochemical detection of trophozoites. Negative (c) and positive (d) macrophages (arrowheads) in mouse hepatic tissue. Negative (e) and positive (f) neutrophils (arrowheads) in mouse skin inflamed by intradermal injection of carrageenan. Bar 30 μm. Harris's haematoxylin counterstained.