Hello Danillo. If your primary antibody was raised in mice (ie, a mouse monoclonal) or rat, and your experimental system is mouse or rat, then your secondary antibody will probably cross-react.

It depends on the secondary antibody you are using. There are good commercial secondary antibodies available that don't cross react between mouse and rat (usually raised from donkey, e.g. from Dianova). However, keep in mind that the more specific you want your secondary antibodies to be, the more you will pay for them. The margin is usually not huge, but noticeable.

Hi,

I work with mouse and rat primary antibodies on regular basis. I use secondary antibodies from Dako, Denmark. I have no cross reactivity so far. I have never tried secondary antibodies from other companies, so I am not sure if they have any cross reactivity.

Hope it helps, Good luck.