Why should I use an IgG control in my IP experiment?

Isotype control antibodies are used to estimate the nonspecific binding of target primary antibodies due to Fc receptor binding or other protein-protein interactions. The IgG control lacks the specific binding region of the antibody, however it matches the class of your primary antibody. When we run IPs, we typically run 2 different negative controls:
1) A bead only control where you incubate your beads with the lysate but do not add any antibody. If you see any pull down, this indicates that your target of interest is non-specifically binding to the beads.
2) An IgG control where you incubate your lysate with the appropriate IgG control antibody instead of your target antibody and then the beads. If you see pull down, it indicates that your target of interest is non-specifically binding to the IgG portion of the antibody.
We recommend using the Rabbit (DA1E) mAb IgG XP® Isotype Control #3900 for rabbit monoclonal antibodies and Normal Rabbit IgG #2729 for rabbit polyclonal antibodies. We also have IgG controls for mouse IgG1 (#5415), IgG2a (#61656 ), IgG2b (#53484), and IgG3 (#37988). 
When you use an IgG control, you will need to match the concentration to the concentration of primary antibody that you are using for pull-down for an accurate comparison.

Last updated: February 26, 2024