Flow Cytometry Triton™ X-100 Permeabilization Protocol for Directly Conjugated Antibodies

A. Solutions and Reagents

All reagents required for this protocol may be efficiently purchased together in our Intracellular Flow Cytometry Kit (Triton™ X-100) #51995, or individually using the catalog numbers listed below.

NOTE: Prepare solutions with reverse osmosis deionized (RODI) or equivalent grade water.

1. 1X Phosphate Buffered Saline (PBS): To prepare 1 L 1X PBS: add 100 ml 10X PBS (#12528) to 900 ml water, mix.
2. 4% Formaldehyde, Methanol-Free (#47746)
3. Cell Permeabilization Buffer: Purchase ready-to-use (#39487) or to prepare 10 ml, add 30 µl Triton™ X-100 to 10 ml Antibody Dilution Buffer. Store at 4°C.
4. Antibody Dilution Buffer: Purchase ready-to-use Flow Cytometry Antibody Dilution Buffer (#13616), or to prepare 100 ml dissolve 0.5 g Bovine Serum Albumin (BSA) (#9998) in 100 ml 1X PBS. Store at 4°C.

NOTE: When including fluorescent cellular dyes in your experiment (including viability dyes, DNA dyes, etc.), please refer to the dye product page for the recommended protocol. Visit www.cellsignal.com for a full listing of cellular dyes validated for use in flow cytometry.

B. Fixation and Permeabilization

NOTE: Adherent cells or tissue should be dissociated and in single-cell suspension prior to fixation.

NOTE: Optimal centrifugation conditions will vary depending upon cell type and reagent volume. Generally, 150-300g for 1-5 minutes will be sufficient to pellet the cells.

NOTE: If using whole blood, lyse red blood cells and wash by centrifugation prior to fixation.

NOTE: Antibodies targeting CD markers or other extracellular proteins may be added prior to fixation if the epitope is disrupted by formaldehyde and/or Triton™ X-100. The antibodies will remain bound to the target of interest during the fixation and permeabilization process. Conduct a small-scale experiment if you are unsure.

1. Pellet cells by centrifugation and remove supernatant.
2. Resuspend cells in approximately 100 µl 4% formaldehyde per 1 million cells. Mix well to dissociate pellet and prevent cross-linking of individual cells.
3. Fix for 15 min at room temperature (20-25°C).
4. Wash by centrifugation with excess 1X PBS. Discard supernatant in appropriate waste container.
5. Resuspend cells in approximately 100 µl Cell Permeabilization Buffer per million cells.
6. Incubate for 10 minutes at room temperature.
7. Proceed with staining or store cells at 4°C in PBS overnight.

C. Immunostaining

NOTE: Count cells using a hemocytometer or alternative method.

1. Aliquot desired number of cells into tubes or wells. (Generally, 5x10⁵ to 1x10⁶ cells per assay).
2. Centrifuge cells and discard supernatant.
3. Resuspend cells in 100 µl of diluted antibody conjugates, prepared in Antibody Dilution Buffer at a recommended dilution or as determined via titration.
4. Incubate for 1 hr at room temperature (20-25°C). Protect from light.
5. Wash by centrifugation in Antibody Dilution Buffer or 1X PBS. Discard supernatant. Repeat.
6. Resuspend cells in 1X PBS and analyze on flow cytometer.