Research paper ZAP-70 and Syk expression in canine lymphoid cells and preliminary results on leukaemia cases M. Mortarino a , M.E. Gelain a , G. Gioia a , E. Ciusani b , C. Bazzocchi a , S. Comazzi a, * a Department of Veterinary Pathology, Hygiene and Health, University of Milan, Via Celoria 10, Milan, Italy b Laboratory of Analysis, Neurological Institute Foundation ‘‘Carlo Besta’’, Via Celoria 11, Milan, Italy 1. Introduction Zeta-chain-associated protein (ZAP-70) and spleen tyrosine kinase (Syk) are non-receptor tyrosine kinases playing an essential role in the signal transduction pathways of hematopoietic Ag receptors that leads to lymphocyte development and activation of immune cells (Van Oers and Weiss, 1995). In humans, ZAP-70 is a 70-kDa protein tyrosine kinase that acts quickly after T-cell activation to propagate signal. The immunoreceptor tyrosine-based activation motif (ITAM) becomes phos- phorylated after engagement of T-cell receptor (TCR), allowing recruitment and phosphorylation of ZAP-70. This mediates the transduction of extracellular stimuli into cellular effector functions, such as lymphokine production, cytolitic activity, proliferation, differentiation and cell Veterinary Immunology and Immunopathology 128 (2009) 395–401 ARTICLE INFO Article history: Received 30 May 2008 Received in revised form 20 November 2008 Accepted 4 December 2008 Keywords: Dog ZAP-70 Syk Real-time PCR Leukocyte Leukaemia ABSTRACT Zeta-chain-associated protein (ZAP-70) and spleen tyrosine kinase (Syk) are structurally and functionally homologous tyrosine kinases playing a role in the T- and B-cell signal transduction. Their activation can lead to lymphokine production, cytolitic activity, antibody secretion, cell proliferation, differentiation, survival and phagocytosis. Anom- alous ZAP-70 and Syk expression is reported to be related to tumor formation and progression, and ZAP-70 immunoreactivity is a good prognostic marker of disease progression in human chronic lymphocytic leukaemia (CLL). Until now, to our knowledge, there are no reports about canine ZAP-70 and Syk expression profiles. In the present study, a RT-PCR procedure for the quali-quantitative evaluation of canine ZAP-70 and Syk transcripts was designed. The expression patterns of canine ZAP-70 and Syk mRNAs were evaluated in canine leukocyte subpopulations and in peripheral whole blood samples from healthy dogs and from dogs with different types of leukaemia. Similarly to humans, normal canine CD4+ and CD8+ T cells showed high expression of ZAP-70, whereas Syk was abundantly expressed in normal CD21+ B cells. The expression profile of ZAP-70 and Syk was markedly different in canine normal and leukaemic blood. Decreased Syk expression was detected in dogs with T-cell CLL, whereas decreased ZAP-70 expression was detected in dogs with B-cell CLL and B-cell acute lymphocytic leukaemia (ALL). The comparison of ZAP-70 and Syk mRNA levels between normal and leukaemic peripheral whole blood showed that the expression ratio ZAP-70/Syk is subjected to modification depending on the leukaemia status of patients. The results of the present work open an interesting topic for leukaemogenesis investigation and are the basis for further studies for a proper evaluation of the potential utility of these parameters for the diagnosis and prognosis of canine T- and B-cell leukaemia. ß 2008 Elsevier B.V. All rights reserved. * Corresponding author at: DIPAV, sez. Patologia Generale Veterinaria e Parassitologia, Via Celoria 10, Milan, Italy. Tel.: +39 02 50318103; fax: +39 02 50318095. E-mail address: stefano.comazzi@unimi.it (S. Comazzi). Contents lists available at ScienceDirect Veterinary Immunology and Immunopathology journal homepage: www.elsevier.com/locate/vetimm 0165-2427/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.vetimm.2008.12.010