Can I use fluorophore conjugated antibody as neutralizing antibody?
In short, yes, most likely.  When an antibody binds to the antigen at a region (epitope) that is needed for the antigen's activity then the activity is reduced (&quot;neutralized&quot;).  The (proper) labeling of an antibody will usually not affect which epitopes it binds to, and so it will work OK (but it may have lower titer than the unlabeled antibody).  As always, there may be some exceptions to this.