Which isotype control should i choose - (Jan/15/2013 )

Dear all please help a FACS noob,
I need to choose isotype control for my surface marker staining. Should i choose isotype control depending on the species i'm labeling, so if i have Ab against human CD44-PE conjugated my control should also be anti human IgG. Also does the choice of type of Ab depend on the specific stained one. For example if my Cd44-PE was IgGk then isotype control should also be IgGk and what is the difference between normal IgG, does it really make a big difference.

Thanks

No, you choose the isotype control according to the species the antibody was raised in. For example, is your anti-human CD44 antibody made in rabbit ? If so, you need rabbit IgG (and your isotype control is not "anti" anything). Since your antibody is primarily conjugated to PE; you need a conjugated rabbit IgG-PE as isotype control. Ideally it should also be the same subtype (IgGk, in your example).