I am not an expert in the use of PAC-1, but I think there has been some misinformation on the list about it and I would like to put in my 2 cents. PAC-1 is an IgM monoclonal that binds to an epitope of GPIIb/IIIa which appears upon activation. The appearance of the epitope requires that GPIIb/IIIa be in its normal configuration and thus requires the presence of calcium. One cannot successfully use PAC-1 on platelets that have been treated with EDTA (citrate is OK), or with fixed platelets (fixation seems to induce artifactual binding of PAC-1 to both resting and activated platelets). The epitope recognized by PAC-1 is not the fibrinogen binding site. As far as I know, there should be no competition between PAC-1 and fibrinogen. Other monoclonals, such as 7E3 do recognize the fibrinogen binding site and will compete with fibrinogen, but I don't think that is true of PAC-1. I hope this is helpful. -------------------------------------------------------------------------- Kenneth A. Ault M.D. Maine Medical Center Research Institute 125 John Roberts Road Suite #8 South Portland ME 04106 Voice: (207) 761-9090 Fax: (207) 761-2130 E-Mail: aultk@mail.mmc.org --------------------------------------------------------------------------
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