SignalStar® Multiplex IHC Frequently Asked Questions
How are the SignalStar Multiplex IHC kits and reagents validated?
CST thoroughly validates each antibody available in the SignalStar Multiplex IHC Panel Builder menu. Various combinations of antibodies are tested through titration and fluorophore pairing, and in both rounds of imaging. Testing is performed on a variety of tumors and tissue types. We also rigorously test the parent antibodies used in the traditional chromogenic assay, as they serve as the foundation of this fluorescent assay. We aren't able to test all multiplex configurations or tissues. Please visit the Technical Support page to find answers for any additional questions.
Does this assay work on frozen tissue?
SignalStar Multiplex IHC antibodies, kits and reagents are specially designed and stringently validated for use in FFPE tissues. They have not been validated for use in frozen tissues.
Do you have human-reactive antibodies available?
Yes, please select “Human” in the first step of the SignalStar Multiplex IHC Panel Builder to see our human-reactive menu.
Do you have mouse-reactive antibodies available?
Yes, please select “Mouse” in the first step of the SignalStar Multiplex IHC Panel Builder to see our mouse-reactive menu.
I don't see my target of interest in your menu of available antibodies. Can I still use it in my panel in some way?
Yes. If you don’t see your target as a SignalStar conjugate, you can select a primary antibody in the Panel Builder and add a SignalStar Secondary Antibody to use unconjugated IHC-validated antibodies instead.
Please note that the SignalStar Secondary Antibodies can only be used in the first round of imaging.
Alternatively, you may perform direct immunofluorescence on the same tissue after the SignalStar assay. The SignalStar® Fluorescence Removal Kit #32722 enables you to remove the fluorescent oligos without stripping off the antibodies, keeping the tissue intact. After that, you may stain the tissue with your conjugated antibody and visualize using direct immunofluorescence.
Can I combine antibodies used in this assay with direct conjugates?
SignalStar Multiplex IHC kits and reagents have been validated for use in combination with direct conjugates. The SignalStar® Fluorescence Removal Kit #32722 enables you to remove the fluorescent signal after SignalStar mIHC in order to stain and visualize direct immunofluorescence. We have found that many direct conjugates against strong cell surface markers work well when used in this manner. Please see our poster for more information. In addition, please see our line of directly conjugated antibodies for use in direct immunofluorescence imaging.
When comparing my SignalStar staining to the chromogenic staining on a serial section, I see more positive cells. How do I know if this excess staining is correct?
During the course of optimization, we've found that fluorescent staining may show higher %-positivity than chromogenic staining. To ensure any excess staining is specific, confirm that the correct subcellular localization and co-localization with other stains are demonstrated. For example, if all CD8+ cells are CD3+, any excess CD8+ staining compared to the chromogenic is most likely correct.
How long after the completion of staining can I wait to image my slides?
For Imaging Round 1, the staining should show robust signal when imaged up to 8 hours post completion of staining. For Imaging Round 2, imaging should be performed as close to the completion of staining as possible, but should remain robust for up to 8 hours.
Do I need to optimize the SignalStar kits and reagents for the type of tissue that I'm using?
The SignalStar Multiplex IHC kits and reagents have been optimized with respect to fluorophore pairing and order of antibodies. As tissues vary in quality and expression level of targets, increasing the concentration of antibodies in your panel by 2-fold or decreasing by 0.5-fold can help achieve optimal signal in your experiments.
What is an appropriate positive control to include in this assay? Are multiple controls necessary?
Any tissue shown to be positive for each marker via chromogenic IHC can serve as a positive control tissue. Each target will therefore require a positive control, which may sometimes necessitate multiple controls. For optimal comparison, the sections should be as close to serial as possible.
Can I perform alternative antigen retrieval methods than those provided in the SignalStar protocol?
For optimal results, we don't recommend deviating from SignalStar protocols. However, if you don't have access to the antigen retrieval method detailed in the protocol, you may try using a microwave, which has shown to result in reduced fluorescent signal. We don't recommend using a microwave when detecting low abundance markers, and can't guarantee your result with this alternative method.
To perform antigen retrieval using a microwave:
- Prepare 250 mL of 1X EDTA unmasking solution by diluting 25 mL of SignalStain® EDTA Unmasking Solution (10X) (#14747) with 225 mL of dH2O.
- Submerse slides in a container of 1X EDTA unmasking solution and heat in a microwave until boiling is initiated, then maintain a rolling boil (5 minutes at full power).
- Follow with 15 minutes at a sub-boiling temperature (95°-98°C). In most microwaves, this equates to 8 minutes at power level 3, then 7 minutes power level 2.
- Remove the container of slides from the microwave and place under a dH2O faucet. Add water directly to the slide container for 5 minutes until all EDTA is replaced by dH2O. No cooling is necessary.
Technical Support
Visit the Technical Support page to search for SignalStar-related troubleshooting information and answers to technical questions.
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U.S. Patent No. 10,781,477, foreign equivalents, and child patents deriving therefrom.