Hello,

You may affinity-purify your antibody using an antigen-bound column. After washing with TBS-Tween, elute your specific antibody wth glycine 0.1 M pH 2 and neutralise immediately with Tris  1M unbuffered. 

Hi,

I'm wondering: are you sure the band at 70kDa is not your protein? Distinguishing 65 of 70 kDa might not be easy, depending on the acrylamide % on your gel. It might be that you see your protein at 70 and a degradation band at 65 kDa.

You can also try to block your antibodies with milk for instance. I suppose you already block the membrane.

Hope it helps

you can go for sequencing of 70 kDA band. it might give you a better clue whether it is a albumin band or your protein of interest.