Cytoplasmic antigen analysis
To detect intracellular antigens it is necessary to permeabilise the cell. Many reagents are available commercially to facilitate this.
- Commercial permeabilisation reagents [PDF - 52KB]
There is a wide variety of different types of intracellular antigen that can be detected by flow cytometry, including:-
Cytokines -Th1Th2 responses
Lymphocytes and splenocytes involved in inflammatory or allergic responses produce a preponderance of IFNgamma or IL-4 respectively. KO murine splenocytes Th1Th2 responses were compared to wild type splenocytes. The KO showed an increased capacity to produce IFNgamma compared to the wild type response whilst IL-2 and IL-4 levels remained the same as the wild type.
Detection of intracellular IL-17
Interleukins (e.g. IL1-17) can be measured intracellularly in lymphocytes after stimulation typically with PMA/ionomycin and blocking the Golgi apparatus with the antibiotic Brefeldin A or Monensin, see protocol.
Activation of whole blood
- Dilute whole blood 1:1 volume to volume (e.g. 100 μl:100 μl) with RPMI1640 medium and mix well.
- Add cell activator or mitogen to the diluted blood e.g. 50 ng/ml PMA + 1μg/ml calcium ionophore or PMA + 1 μM ionomycin (final concentration) in the presence of a protein calcium inhibitor such as Golgi plug containing brefeldin A ( ng/ml).
- Vortex briefly to mix. Aliquot 200μl into 12 x 75 plastic tubes. Incubate for 4-6 h in 5% CO2 at 37˚ C.
- Add 2ml of Pharmlyse (eBioScience), vortex and incubate for 10 min at RT in the dark.
- Spin 5 min, 500g.
- Aspirate the supernatant, Wash 1X in staining buffer. Spin 5 min at 500g. Aspirate the supernatant.
- Continue with staining after adding 50μl PBS to each tube.
Transcription factors
Foxp3 the self-reactive transcription factor, the master regulator involved in lymphocyte development and function of regulatory T cells can be measured intracellularly by flow cytometry, see protocol.
Foxp3 Intracellular staining in whole blood
- To 100 μl whole blood add anti mouse CD3FITC, CD4APC, CD25PEor mouse isotypePE (1 mg/ml). Mix on Vortex and incubate for 20 min at RT.
- Add 2ml of Pharmlyse (Becton Dickinson), vortex and incubate for 10 min at RT in the dark.
- Spin 5 min, 500g.
- Aspirate the supernatant.
- Add 100 ml of Fix solution A (Caltag Fix and Perm Kit), mix on vortex and incubate for 15 min at RT.
- Add PBS and spin 5 min, 500g.
- Aspirate the supernatant.
- Add 100 ml of Perm solution B (Caltag Fix and Perm Kit). Mix on Vortex and incubate for 15 min at RT.
- Add PBS and spin 5 min, 500g.
- Aspirate the supernatant.
- Add anti mouse Foxp3PB(0.5 mg) or mouse isotypePB (0.5 mg) to cell pellets. Mix on Vortex and incubate for 30 min on ice.
- Add PBS and spin 5 min, 500g.
- Aspirate the supernatant.
- Add PBS <0.5ml.
- Collect >25,000 events.
Cyclins
The intracellular detection of cyclins can be combined with cell cycle analysis, see cell cycle analysis section.
Apoptotic factors
The pro-apoptotic factor, bak undergoes a conformational change when activated during apoptosis involving the mitochondria. The degree of bak activation can be determined intra- cellularly by use of mcab that detects the activated form of bak, see protocol.
Pro-Apoptotic Factor Intracellular Labelling Protocol
- Pelleted cells fixed with 0.25% paraformaldehdye for 1 hour on ice.
- Cells were washed in PBS.
- Primary mcab (1 mg) was added to cell pellets permeabilised in 0.01% saponin (Sigma) and incubated on ice for 30 mins.
- Cells were washed in PBS/0.01% Saponin.
- Secondary antibody (0.5 mg) were added to cell pellets and incubated for 30 mins on ice.
- Cells were washed in PBS/0.01% Saponin and resuspended in 0.5 ml PBS.
- At least 10,000 events were analysed by flow cytometry.
- cytokines e.g. IL-17
- apoptotic factors e.g. bak activation
- cyclins
- Transcription Factors e.g. Foxp3