Anti-chemotactic activity in the secretory/excretory products of Lepeophtheirus salmonis.

The ectoparasite, Lepeophtheirus salmonis (Kroyer 1837), is effective at avoiding elimination from its host, Atlantic salmon, Salmo salar L., by inhibiting the recruitment of immune cells to the site of attachment. In other ectoparasitic arthropods, numerous factors have been identified that bind or neutralize chemokines preventing their interaction with receptors on the surfaces of immune cells. To determine if L. salmonis is utilizing a similar mechanism of immune modulation, the chemotactic activity of peripheral blood leukocytes (PBL) to leukotriene B4 (LTB4) and the secreted/excreted products (SEPs) of the sea louse were investigated in vitro. The results showed that incubation of LTB4 with SEPs reduced leukocyte migration compared to LTB4 immune stimulation alone. Data suggests that one of the mechanisms L. salmonis may be using to regulate immune cell recruitment in Atlantic salmon is by inhibiting or neutralizing the activity of chemokines.