polyclonal antibodies go bad - when stored at -80???? (Dec/11/2007 )

Has anyone ever had an antibody that was stored at -80 go bad? The antibodies in question are polyclonal antibodies in the crude serum. They are about 2 years old, and I don't believe that anything was added to them when they were frozen. I've been testing them lately on western blots and I haven't been able to see anything. I know that my proteins are present on my blot because I can detect a GFP tagged version of my protein with a GFP antibody. I haven't changed anything about my protocol from when I previously was able to get a signal. I really fear that the antibodies have gone bad (have degraded or just aren't active anymore) and that I will need to make new ones, but my PI says that he's never had an antibody go bad when the crude sera is stored at -80. If anyone else has had this happen, I'd appreciate your comments as right now I feel like my PI doesn't believe me.

You surely looked at that, but I'll try asking anyway

Is the molecular weight of the band detected with your GFP antibody the same as the band your home made antobody should recognize? If not, your protein may have lost the tag by an unknown mechanism.

We have antibodies over 5 years old at -20 C and they still work well. I have never heard of an antibody "fading" at -80.

You surely looked at that, but I'll try asking anyway

Is the molecular weight of the band detected with your GFP antibody the same as the band your home made antobody should recognize? If not, your protein may have lost the tag by an unknown mechanism.

We have antibodies over 5 years old at -20 C and they still work well. I have never heard of an antibody "fading" at -80.

How about the secondary antibodies? May be they are the culprit.

I agree with Scolix, I would also have put a bet on a bad secondary antibody.
I had several antibodies at -20°C, even diluted, that were still working.
The only antibody I store at -20°C with glycerol are the conjugated one.