Vet. Res. 35 (2004) 39-51
DOI: 10.1051/vetres:2003041

Immunophenotypic characterization and depletion of pulmonary intravascular macrophages of horses

Om P. Parbhakar^a, Tanya Duke^b, Hugh G.G. Townsend^c and Baljit Singh<sup>a

a</sup>  Departments of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, 52 Campus Drive, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada
^b  Small Animal Clinical Sciences, Western College of Veterinary Medicine, 52 Campus Drive, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada
^c  Large Animal Clinical Sciences, Western College of Veterinary Medicine, 52 Campus Drive, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada

(Received 10 February 2003; accepted 30 June 2003)

Abstract - Pulmonary intravascular macrophages (PIMs) are present in horses and are believed to increase their sensitivity to endotoxin-induced cardio-pulmonary shock. However, owing to a lack of a marker for PIMs and the inability to isolate them, their precise contributions in the horse remain unknown. We designed this study to identify an immuno-phenotypic marker for PIMs and to develop a protocol for their transient depletion with gadolinium chloride (GC). GC is a lanthanide that has been used to deplete liver and lung macrophages. The horses (N = 15) were divided into control (n = 5) and GC-treated (n = 10) groups and the lung samples were examined by routine and immunocytochemical light and electron microscopy. GC-treated horses were euthanized at 48 h (n = 6) and 72 h (n = 4) post-treatment. The PIMs reacted with MAC-387 but not with ED-1 and CD-68 anti-macrophage antibodies. GC reduced the number of PIMs in horses at 48 and 72 h compared with the control (p < 0.05). There were increased intravascular TUNEL-positive cells in GC-treated horses and electron microscopy showed apoptotic PIMs in these horses. These data show that MAC-387 is a reliable marker for PIMs and GC is a safe tool to reduce the number of PIMs.

Key words: PIMs / gadolinium / MAC-387 / apoptosis / immunohistology / immuno-electron microscopy / TUNEL


© INRA, EDP Sciences 2004