Figure 1.

Immune responses against Nippostrongylus brasiliensis (Nb) infection in the skin. Nb leaves the skin and enters the blood and lymphatic vessels within 20 minutes of primary infection. In IL-5 transgenic mice, eosinophils are activated by overexpression of IL-5, and produce the anti-helminthic enzyme, major basic protein (MBP), causing Nb parasites to arrest in the skin lesion during primary infection. However, Nb antigens activate basophils during secondary infection, and correspondingly activate monocytes/macrophages to promote M2-type macrophage differentiation. Activated M2-type macrophages then secrete the anti-nematode enzyme, Arginase-I. Eosinophils are also accumulated in the skin, but the role of these accumulated eosinophils is not yet known. Depletion of basophils allows for Nb parasites to leave the skin, but eosinophils still infiltrate the tissue during secondary infection.