I'm facing challenges with performing immunofluorescence for TGF-beta along with GFAP in my 4% PFA-fixed brain samples (frozen sections). While GFAP is yielding satisfactory results, TGF-beta isn't performing well. I'm using the Thermo Fisher antibody with the code PA1-29032. The antigen retrieval I've been employing is citrate buffer at 90ºC, which has worked for my other stainings. Any tips on troubleshooting this issue?