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REACTIVITY SENSITIVITY MW (kDa) Isotype
H M Endogenous 42 Rabbit IgG
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Flow cytometric analysis of MCF-7 cells (blue) or THP-1 cells (green) using PU.1 (9G7) Rabbit mAb (Alexa Fluor® 488 Conjugate).

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Flow Cytometry General Protocol

If using whole blood, please follow the Flow Cytometry Whole Blood Protocol.

A. Solutions and Reagents

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

  1. 20X Phosphate Buffered Saline (PBS): (#9808) To prepare 1 L 1X PBS: add 50 ml 20X PBS to 950 ml dH2O, mix.
  2. 16% Formaldehyde (methanol free).
  3. 100% methanol.
  4. Incubation Buffer: Dissolve 0.5 g Bovine Serum Albumin (BSA) (#9998) in 100 ml 1X PBS. Store at 4°C.

B. Fixation

  1. Collect cells by centrifugation and aspirate supernatant.
  2. Resuspend cells in 0.5–1 ml 1X PBS. Add formaldehyde to obtain a final concentration of 4%.
  3. Fix for 10 min at 37°C.
  4. Chill tubes on ice for 1 min.
  5. For extracellular staining with antibodies that do not require permeabilization, proceed to immunostaining (Section D) or store cells in PBS with 0.1% sodium azide at 4°C; for intracellular staining, proceed to permeabilization (Section C).

C. Permeabilization

NOTE: This step is critical for many CST antibodies.

  1. Permeabilize cells by adding ice-cold 100% methanol slowly to pre-chilled cells, while gently vortexing, to a final concentration of 90% methanol. Alternatively, remove fix prior to permeabilization by centrifugation and resuspend in 90% methanol as described above.
  2. Incubate 30 min on ice.
  3. Proceed with immunostaining (Section D) or store cells at -20°C in 90% methanol.

D. Immunostaining

NOTE: Account for isotype matched controls for monoclonal antibodies or species matched IgG for polyclonal antibodies. Count cells using a hemocytometer or alternative method.

  1. Aliquot 0.5–1 x 106 cells into each assay tube (by volume).
  2. Add 2–3 ml incubation buffer to each tube and wash by centrifugation. Repeat.
  3. Resuspend cells in 100 µl of diluted primary antibody (prepared in incubation buffer at the recommended dilution).
  4. Incubate for 1 hr at room temperature.
  5. Wash by centrifugation in 2–3 ml incubation buffer.
  6. Resuspend cells in 0.5 ml PBS and analyze on flow cytometer; alternatively, for DNA staining, proceed to optional DNA stain (Section E).

E. Optional DNA Dye

  1. Resuspend cells in 0.5 ml of DNA dye (e.g. Propidium Iodide (PI)/RNase Staining Solution #4087).
  2. Incubate for at least 30 min at room temperature.
  3. Analyze cells in DNA staining solution on flow cytometer.

posted July 2009

revised September 2013

Flow Cytometry Whole Blood Protocol

If using cell lines, please follow the Flow Cytometry General Protocol.

A. Solutions and Reagents

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

  1. 20X Phosphate Buffered Saline (PBS): (#9808) To prepare 1 L 1X PBS: add 50 ml 20X PBS to 950 ml dH2O, mix.
  2. 16% Formaldehyde (methanol free).
  3. Triton™ X-100: To prepare 50 ml of 0.1% Triton™ X-100 add 50 μl Triton™ X-100 to 50 ml 1 X PBS and mix well.
  4. 50% methanol.
  5. Incubation Buffer: Dissolve 0.5 g Bovine Serum Albumin (BSA) (#9998) in 100 ml 1X PBS. Store at 4°C.

B. Preparation of Whole Blood (fixation, lysis, and permeabilization) for Immunostaining

  1. Aliquot 100 μl fresh whole blood per assay tube.
  2. OPTIONAL: Place tubes in rack in 37°C water bath for short-term treatments with ligands, inhibitors, drugs, etc.
  3. Add 65 μl of 10% formaldehyde to each tube.
  4. Vortex briefly and let stand for 15 min at room temperature.
  5. Add 1 ml of 0.1% Triton™ X-100 to each tube.
  6. Vortex and let stand for 30 min at room temperature.
  7. Add 1 ml incubation buffer.
  8. Pellet cells by centrifugation and aspirate supernatant.
  9. Repeat steps 7 and 8.
  10. Resuspend cells in ice-cold 50% methanol in PBS (store methanol solution at -20°C until use).
  11. Incubate at least 10 min on ice.
  12. Proceed with staining or store cells at -20°C in 50% methanol.

C. Staining Using Conjugated Primary Antibodies

NOTE: Account for isotype-matched controls for monoclonal antibodies or species matched IgG for polyclonal antibodies.

  1. Add 2–3 ml incubation buffer to each tube and rinse by centrifugation. Repeat.
  2. Add primary antibodies diluted as recommended on datasheet or product webpage in incubation buffer.
  3. Incubate for 1 hr at room temperature.
  4. Wash by centrifugation in 2–3 ml incubation buffer.
  5. Resuspend cells in 0.5 ml PBS and analyze on flow cytometer.

Reference: Chow S, Hedley D, Grom P, Magari R, Jacobberger JW, Shankey TV (2005) Whole blood fixation and permeabilization protocol with red blood cell lysis for flow cytometry of intracellular phosphorylated epitopes in leukocyte subpopulations. Cytometry A 67(1), 4–17.

posted November 2008

revised September 2013

protocol id: 407

Product Usage Information

Application Dilutions
Flow Cytometry 1:50

Storage: Supplied in PBS (pH 7.2), less than 0.1% sodium azide and 2 mg/ml BSA. Store at 4°C. Do not aliquot the antibody. Protect from light. Do not freeze.

Specificity / Sensitivity

PU.1 (9G7) Rabbit mAb (Alexa Fluor® 488 Conjugate) detects endogenous levels of total PU.1 protein. This antibody does not cross react with other Ets family members.


Species Reactivity: Human, Mouse
Species predicted to react based on 100% sequence homology: Monkey, Pig

Source / Purification

Monoclonal antibody is produced by immunizing animals with a synthetic peptide corresponding to the sequence of human PU.1 protein. The antibody was conjugated to Alexa Fluor® 488 under optimal conditions with an F/P ratio of 2-6.

Product Description

This Cell Signaling Technology antibody is conjugated to Alexa Fluor® 488 fluorescent dye and tested in-house for direct flow cytometric analysis of human cells. The unconjugated antibody #2258 reacts with human and mouse PU.1 protein. CST expects that PU.1 (9G7) Rabbit mAb (Alexa Fluor® 488 Conjugate) will also recognize PU.1 in these species.


PU.1 is a member of the Ets family of transcription factors and activates target genes through the purine-rich PU-box (1). PU.1 plays a pivotal role in the differentiation of myeloid cells and lymphocytes and is expressed in several hematopoietic cells including B lymphocytes, macrophages, neutrophils, mast cells, early erythroid cells and megakaryocytes (1,2). The concentration of PU.1 is critical for both the determination of hematopoietic cell lineage and the regulation of differentiation versus stem cell proliferation (3,4). In addition, PU.1 activity is influenced by phosphorylation and interactions with other hematopoietic transcription factors. Phosphorylation of PU.1 at Ser146 by CK2 promotes binding to IRF4 and synergistic activation through the immunoglobulin κ 3' enhancer (5). Treatment of pro-B cells with IL-3 leads to phosphorylation of PU.1 at Ser140, resulting in increased PU.1 activity and activation of the anti-apoptotic gene MCL-1 (6). GATA1 binding blocks PU.1 activity during erythroid cell development (7). Overexpression of PU.1 resulting from proviral insertion during Friend virus infection can induce erythroleukemia, while reduced expression has been associated with acute myeloid leukemia (8).


1.  Lloberas, J. et al. (1999) Immunol. Today 20, 184-189.

2.  Klemsz, M.J. et al. (1990) Cell 61, 113-124.

3.  Dahl, R. and Simon, M.C. (2003) Blood Cells Mol. Dis. 31, 229-233.

4.  DeKoter, R.P. and Singh, H. (2000) Science 288, 1439-1441.

5.  Pongubala, J.M. et al. (1993) Science 259, 1622-1625.

6.  Wang, J.M. et al. (2003) Mol. Cell Biol. 23, 1896-1909.

7.  Zhang, P. et al. (1999) Proc. Natl. Acad. Sci. USA 96, 8705-8710.

8.  Moreau-Gachelin, F. et al. (1998) Nature 331, 277-280.


Entrez-Gene Id 6688
Swiss-Prot Acc. P17947


For Research Use Only. Not For Use In Diagnostic Procedures.
Cell Signaling Technology® is a trademark of Cell Signaling Technology, Inc.
The Alexa Fluor® dye antibody conjugates in this product are sold under license from Life Technologies Corporation for research use only, except for use in combination with DNA microarrays. The Alexa Fluor® dyes (except for Alexa Fluor® 430 dye) are covered by pending and issued patents. Alexa Fluor® is a registered trademark of Molecular Probes, Inc.
U.S. Patent No. 5,675,063.