Activation of immunological responses in Litopenaeus setiferus hemocytes by a hemocyanin like-lectin

In order to identify the specific role of humoral lectins in crustaceans' immune response, we evaluated the effect of the 291 kDa hemocyanin-like lectin from Litopenaeus setiferus (LsL) on its own hemocytes. LsL binds 5.6% of circulating non-activated hemocytes, but is able to recognize 85% of total adhered (activated) hemocytes, showing filipodia and pseudopodia, inducing the production of reactive oxygen intermediates (ROIs) in a time- and dose-dependent manner (100 ng/105 cells/20 min). This effect was inhibited specifically by N-acetylated sugars (NeuAc, GalNAc or GlcNAc), as well as by superoxide dismutase (SOD), acetylsalicylic, and mefenamic acid. In hemocytes, LsL also induced higher ROIs production than Zymozan (p > 0.05). The receptor for LsL in the hemocytes membrane is a glycoprotein of 61 and 52 kDa per subunit, as determined by western blot. Our results suggest that LsL participates in the activation of oxidative immune responses of granular hemocytes induced by NADPH and other oxidative pathways through a specific membrane receptor.