Invitrogen isotype specific secondary antibodies - (Feb/11/2011 )

Dear friends,
I have a problem with the detection of a primary antibody anti-p63 (nuclear protein of basal cells in epidermis).
The primary antibody is a Santa Cruz monoclonal mouse IgG2a anti-human p63 (4A4 clone).
I used different types of secondary antibodies:

1- Dako rabbit anti-mouse IgG FITC ═══> it works!
2- Invitrogen goat anti-mouse IgG2a Alexa488══╗
3- Invitrogen goat anti-mouse IgG2a Alexa633══╩═══> they do not work, the same way: they look like to be specific for all of the epidermis layers, particularily the lucid layer. Nuclei appear negative.

Now, do you think it could be a problem of the primary or the two secondary antibodies from Invitrogen (I guess they are the same lot of anti-IgG2a, differently conjugated)?

Thank you for your help!

The Dako ab is binding many areas of the heavy chain and possibly the light chain as well. The others are specific for that subclass so only one particular region is being bound.