In some cases NaN3 causes problems with HRP reactions.  (alas most of my
assays are with AP substrates so I don't know under which conditions it
causes problems)  My advice is to try the assay with the CD31 and GAR
diluted in plain 0.3%BSA, if it works you have an answer. Its fairly common
for NaN3 to be included in commercial antibody buffers.  But that is then
diluted in blocking buffer for the assay and then the secondary doesn't have
added NaN3.

Amanda Gifford
CTL Immunotherapies Corp
HTL (ASCP)

agifford@ctl.net