I have been performing western blots to detect IL1a from porcine tissue samples. I've extracted my protein using non-denaturing lysis buffer. Before loading in a gel, I boil my samples with 10% B-mercaptoethanol for 5 minutes (100C). I've used a protein standard (recombinant porcine IL1a) and the bands for the recombinant protein show up where they are supposed to (17kDa). However, the bands that appear from my samples are not present for all samples, and appear at ~65-68kDa. I am getting one band at a lower molecular weight from the lane that presents the strongest 68kDa band.
What is going on? Why is my protein so high? I've used both monoclonal and polyclonal antibodies, both with similar results.