ABSTRACT
The initiation and regulation of the Chondrichthyan immune system will require intercellular communication, with secretion of signaling molecules that will bind to specific receptors on target cells, to elicit a downstream intracellular cascade and response. In mammals, an important group of such signaling molecules are the cytokines, which are generally small proteins (or glycoproteins), that are secreted by different leucocyte types, and belong to a number of cytokine families, including the interleukins, 124interferons, tumor necrosis factors, transforming growth factors, chemokines, and colony-stimulating factors. Although it is still early days for the determination of cytokine function in Chondrichthyans, significant progress was made in cytokine gene discovery, and this chapter summarizes the work that was carried out to date on characterizing these molecules, mainly discovered by exploiting expressed sequence tag (EST) sequences from selected cartilaginous fish species and by searching the elephant shark, Callorhinchus milii, and little skate, Leucoraja erinacea, genome databases.
