I have been working with mouse tissue for quite some time. It has recently come to my attention that the goat anti-mouse antibody (GE) I have been using causes very crisp, strong bands at 50 and 25 kDa in the absence of primary antibody. This also happens, though not nearly as strongly (about 1/10th as strong) in rat tissue. I also saw this using a donkey anti-mouse (Jackson), only much stronger and even more bands. I have not had a chance yet to try no primary with these samples plus a rabbit secondary, but I suspect the bands would not show up, based on some other blots where I used a rabbit secondary and there are no bands at 50 kda.
50 and 25 seem like heavy and light chain fragments, but one professor I talked to said if it really was endogenous antibodies it would look like a big smear and not sharp bands. That is about all I have right now.
Any input would be greatly appreciated.
False positive from Endogenous Antibodies?
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