1. Department of Zoology, Faculty of Science, Charles University in Prague, Viničná 7, 128 44 Prague, Czech Republic;
2. Department of Immunogenetics, Institute of Animal Biochemistry and Genetics, Slovak Academy of Sciences, 900 28 Ivanka pri Dunaji, Slovak Republic
3. Division of Immunology, School of Infection and Host Defence, Duncan Building, University of Liverpool, L69 3BX, Liverpool, U.K.