LYZ and argyrophilic grain disease: While lysozyme has been shown to change in response to other parasites such as Ichthyophthirius multifiliis and Ceratomyxa shasta (Alvarez-Pellitero, 2008), the current results suggest that serum lysozyme may not play a major role in AGD as suggested by Gross et al. (2005) who proposed that, as lysozyme levels are regulated by peripheral blood leucocytes, infection by N. perurans may not stimulate these cells in the serum to elicit a response.