One misconception is that IF is performed on frozen tissues, while IHC is performed on FFPE tissues. However, IHC and IF use all of the same conditions (starting sample, antigen retrieval, blocking, primary antibody), except IHC uses chromogens while IF uses fluorophores for detection. Therefore, the difference is in the detection method, not the starting sample. IHC and IF can both be used on frozen or FFPE tissues; however, you tend to get more autofluorescence with FFPE tissues, which can be an issue for IF. Moreover, IHC can have limitations when staining for multiple markers or assessing coexpression. If an antibody works well for IHC, it should also work well for IF and vice versa. If it works well for just one and not the other, your issue lies in your chromogenic or fluorescent detection of the positive signal. However, just because an antibody detects signal well in frozen tissue section does not mean it will work well for FFPE tissues. This is because formalin fixation facilitates protein cross-linking, which can change epitopes from their original structure. Antigen retrieval methods can break these cross-links in various ways, but the epitope may not resemble that of the original protein structure. If this is true, an antibody may bind well to frozen tissue targets but not FFPE tissue targets, or vice versa.

When you buy antibody, company recommends which method, it will work. If it will work for IHC or WB etc. In my opinion, any antibody works for IF should work for IHC. IF is done on cryo sections where antigen retrieval is not needed, in general. But IHC is done on paraffin sections, you need to retrieve antigen, Many methods of antigen retrieval are available. Which one is good, you need to figure out first.

One misconception is that IF is performed on frozen tissues, while IHC is performed on FFPE tissues. However, IHC and IF use all of the same conditions (starting sample, antigen retrieval, blocking, primary antibody), except IHC uses chromogens while IF uses fluorophores for detection. Therefore, the difference is in the detection method, not the starting sample. IHC and IF can both be used on frozen or FFPE tissues; however, you tend to get more autofluorescence with FFPE tissues, which can be an issue for IF. Moreover, IHC can have limitations when staining for multiple markers or assessing coexpression. If an antibody works well for IHC, it should also work well for IF and vice versa. If it works well for just one and not the other, your issue lies in your chromogenic or fluorescent detection of the positive signal. However, just because an antibody detects signal well in frozen tissue section does not mean it will work well for FFPE tissues. This is because formalin fixation facilitates protein cross-linking, which can change epitopes from their original structure. Antigen retrieval methods can break these cross-links in various ways, but the epitope may not resemble that of the original protein structure. If this is true, an antibody may bind well to frozen tissue targets but not FFPE tissue targets, or vice versa.

For IHC you normally use a amplification system with HRP and for example DAB. In IF conjugated antibodies might result in a weaker signal. Therefore you might consider to use an amplification system such as TSA or an Amplification-tree with Biotin/Streptavidin.