Tissue factor around dermal vessels has bound factor VII in the absence of injury.
BACKGROUND
'Idling' or ongoing low-level activity of the tissue factor (TF) pathway is a postulated mechanism by which the coagulation process can become active without a lag period at sites of injury.


OBJECTIVE
To determine whether TF around cutaneous vessels has bound factor VIIa in the absence of injury, and thus could participate in the idling process.


METHODS
Immunostaining of mouse skin with antibodies against a 15-residue peptide from the sequence of mouse TF, and against the whole extracellular portion of TF.


RESULTS
The whole TF antibody recognized TF in squamous epithelium and around vessels in the dermis. By contrast, the monospecific antibody only recognized TF in the squamous epithelium, but not around vessels. We also found that biotinylated, active site-inhibited FVIIa (FVIIai) bound to tissue sections in the same areas in which TF was recognized by the monospecific antibody (squamous epithelium), but did not bind around vessels. Molecular modeling revealed that FVIIa and FX binding to TF masked a significant part of the surface of the target peptide.


CONCLUSIONS
In the aggregate, these data are most consistent with the interpretation that TF in perivascular sites has bound FVIIa, even in the absence of any injury. The presence of endogenously bound FVIIa prevents the subsequent binding of the monospecific antibody or exogenous FVIIai to perivascular TF.
Hoffman
M
M
Duke University Medical Center, Durham, NC, USA. maureane@med.unc.edu
Colina
C M
CM
McDonald
A G
AG
Arepally
G M
GM
Pedersen
L
L
Monroe
D M
DM
D000818:Animals; D001777:Blood Coagulation / Q000502:physiology; D005167:Factor VII / Q000737:chemistry / Q000378:metabolism*; D015942:Factor VIIa / Q000737:chemistry / Q000378:metabolism; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D046912:Multiprotein Complexes; D011485:Protein Binding; D012867:Skin / Q000098:blood supply* / Q000378:metabolism*; D013925:Thromboplastin / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D014018:Tissue Distribution
D046912:Multiprotein Complexes; D005167:Factor VII; D013925:Thromboplastin; D015942:Factor VIIa