Comparison of MAP and tyrosine kinase signaling in heterophils from commercial and wild-type turkeys

Abstract

Protein tyrosine and mitogen-activated kinases are crucial mediators of the host innate immune response, conferring signals from surface receptors on the host cell to the nucleus of the cell where gene expression occurs. Heterophils were isolated from wild-type Rio Grande turkeys and a commercial line of turkeys (Line A) on days 4 and 7 post-hatch. Heterophils were stimulated for 1 h with Salmonella enteritidis (SE) or opsonized SE (OPSE). After stimulation, cells were lysed and lysates were tested for mitogen-activated protein kinase (MAPK) activity. Specifically, phosphorylation of extracellular signal-regulated protein kinase (ERK1/2) and p38 MAPK phosphorylation were assayed using commercially available ELISA kits. Total protein tyrosine kinase (PTK) activity was also assayed. On both days 4 and 7 post-hatch, heterophils from Rio Grande turkeys had significantly higher levels of ERK 1/2 and p38 MAPK kinase activity upon stimulation with either SE or OPSE ( p < 0.001 ). Likewise, PTK values on days 4 and 7 in Rio Grande turkey heterophils were significantly higher upon stimulation with SE than with OPSE and were significantly ( p < 0.001 ) higher than PTK levels in Line A upon SE and OPSE stimulation. The data presented supports previous heterophil functional comparison studies wherein heterophils from Rio Grande turkeys had higher levels of oxidative burst and degranulation activities as compared to the activity observed in commercial Line A heterophils. This suggests that the regulation and control of these functions are mediated by protein tyrosine and mitogen-activated kinases. Furthermore, the data suggest that selection of commercial lines of turkeys for larger, heavier bodies, and faster growth may be associated with subsequent selection for decreased innate immune functions related to intracellular signaling mechanisms and possibly a subsequent increase in susceptibility to disease.