Invitrogen™ CELLection™ Pan Mouse IgG Kit

The CELLection kits contain Dynabeads magnetic beads coated with a DNA linker (either via streptavidin or via an antibody for cell isolation) and a DNase enzyme for bead release. After the beads capture the target cells (either directly or indirectly), the cells are released by DNAse treatment to cleave the linker. As a result, the target cells are released from the Dynabeads magnetic beads, but still linked with capture antibody.

We offer three Dynabeads CELLection cell isolation kits:

- CELLection Epithelial Enrich Kit (Cat. No. 16203) contains Dynabeads magnetic beads coupled with anti-EpCAM monoclonal antibody
- CELLection Biotin Binder Kit (Cat. No. 11533D) is used for positive isolation of target cells with your own biotinylated antibody
- CELLection Pan Mouse IgG Kit (Cat. No. 11531D) is used for isolation of target cells with your own mouse IgGs

There are three methods to remove the Dynabeads magnetic beads from the isolated cells:

1. DETACHaBEAD Kits (positive isolation) - where the release agent is a polyclonal anti-Fab reagent outcompeting the binding of the bead-bound antibody on the cell, giving both antibody- and bead-free cells. Kits are available for Human CD4+ and CD8+ T cells, CD19+ B cells, and CD34+ hematopoietic stem cells.
2. CELLection Kits - where the release agent is a DNase enzyme, digesting the DNA-linker between the antibody and the bead, ultimately leading to bead-free cells. Kits are available for human EpCAM (Ber-EP4) epithelial cells and streptavidin (binding any biotinylated antibodies).
3. FlowComp Kits - where the release reagent is biotin that is out-competing the des-biotinylated antibody coupled onto the beads. Available for human and mouse whole T cells, the T cells subsets CD4+ and CD8+, and human monocytes.

Thaw cells in their cryovial in a 37 degrees C water bath until a small ice-clump is left. Transfer the cells gently to a fresh 10-15 mL tube immediately after the cells are thawed and add 10 mL 20% FCS/human serum in droplets to the cells while gentle pipetting. Avoid air bubbles. Work fast. Centrifuge the cells 200 X g, 8 minutes. Discard the supernatant. Resuspend in the appropriate buffer/media.

In general, freezing medium (10% DMSO and 90% FCS) or Gibco Recovery Cell Culture Freezing Medium (Cat. No. 12648-010) work well. Some cells will always die during the freezing process. In addition, freezing and thawing will cause some cells to lyse. The protocol to freeze mammalian cells using Gibco Recovery medium is as follows:

1. Thaw Recovery Cell Culture Freezing Medium, mix well, and keep at 2-8 degrees C until use.
2. For suspension cells proceed to step 3. For adherent cells, gently detach cells from the substrate on which they are growing using a suitable dissociation reagent such as Gibco TrypLE reagent. Resuspend cells in the complete medium required for that cell type.
3. Transfer cell suspension to a sterile 15 mL centrifuge tube.
4. Determine the viable cell density and percent viability using a Countess Automated Cell Counter (similar automated or manual methods may be used) and calculate the required volume of Recovery Cell Culture Freezing Medium to give a final cell density of 1 X 10E6 to 1 X 10E7 cells/mL.
5. Centrifuge cell suspension at 100-200 x g for 5-10 minutes. Aseptically decant supernatant without disturbing the cell pellet. Note: Centrifugation speed and duration may vary depending on cell type.
6. Resuspend the cell pellet in (2- 8 degrees C) chilled Recovery Cell Culture Freezing Medium at recommended viable cell density for specific cell type (typically 1 X 10E6 cells/mL or greater).
7. Dispense aliquots of cell suspension (mix frequently to maintain a homogeneous cell suspension) into cryovials according to the manufacturer's specifications (i.e., 1.5 mL in a 2 mL cryovial).
8. Achieve cryopreservation in an automated or manual controlled rate freezing apparatus following standard procedures (approximately 1 degree C decrease per minute).
9. Transfer frozen cells to liquid nitrogen, (vapor phase); storage at -200 degrees C to -125 degrees C is recommended.

Bone marrow needs to be washed and diluted prior to addition of Dynabeads magnetic beads to make the sample less viscous. Washing and DNase treatment is recommended for preparing bone marrow cells prior to cell isolation using Dynabeads magnetic beads:

- Mix 2 mL (10E7-10E8 cells) bone marrow with 2 ml PBS w/ 0.1% BSA + 0.6% Na-citrate.
- Centrifuge at 600 g for 8 min at 18-25 degrees C.
- Discard the supernatant and resuspend to 5 mL with PBS w/ 0.1% BSA + 1mM CaCl₂ + 0.5 mM MgCl₂.
- Add 600 Kunitz units DNase I (120 Kunitz units DNase I per milliliter).
- Incubate cells for 30 minutes at 18-25 degrees C with both gentle tilting and rotation.
- Centrifuge cell suspension for 8 minutes, 600 x g, at 18-25 degrees C.
- Discard supernatant and resuspend cell pellet in 5 mL PBS w/ 0.1% BSA.
- Centrifuge cell suspension for 8 minutes, 600 x g, at 18-25 degrees C.
- Discard supernatant and resuspend at 1 x 10E8 cells per milliliter in RPMI 1640 / 1% FCS

Follow standard tissue preparations using enzymes and mechanical disruption to get a single-cell suspension. Eliminate large aggregates by sieving the digested cell suspension through a cell strainer or filter through a 30 µm filter. Disruption of tissue normally results in some cell death and release of DNA. Free DNA will impair cell capture, recovery, and purity. DNase I treatment is performed by incubating the cell suspension in PBS with 0.1% BSA + 1 mM CaCl₂ + 0.5 mM MgCl₂ and 120 Kunitz units DNase I per ml at 18-25 degrees C for 30 min. (For CELLection products, wash cells to remove DNase before adding the beads.)

Mononuclear cells (MNC), also known as peripheral blood mononuclear cells (PBMC), are prepared from whole blood, buffy coat, bone marrow, or umbilical cord blood by density gradient separation. The following protocol can be used for standard MNC preparation for positive isolation or depletion protocols:

1. Collect blood sample with anticoagulant present (EDTA, ACD, heparin). Dilute peripheral blood 1 + 1, buffy coat 1 + 2, bone marrow 1 + 1 and umbilical cord blood 1 + 3 in PBS w/ 0.1% BSA + 0.6% Na-citrate or 2 mM EDTA.
2. Layer up to 35 mL of the diluted sample over 15 mL gradient medium (such as Ficoll or Lymphoprep solution) in a 50 mL tube.
3. Centrifuge for 400 x g for 30-40 minutes at 18-20 degrees C. If blood has been stored for more than 2 hours, increase centrifugation time by 10 min.
4. Collect MNC from the interface and transfer cells to a 50 mL tube.
5. Wash MNC three times with PBS w/0.1% BSA by centrifugation at 300 x g for 8 min at 2-8 degrees C.
6. Resuspend the cells to 1 x 10E7 cells per milliliter in PBS with 0.1% BSA and cool to 2-8 degrees C.
Note: MNC contain T cells (50%), B cells (5-10%), NK cells (5-10%), and monocytes (30%) without granulocytes and very few platelets.

For use with Untouched/negative isolation kits, the following protocol is recommended to obtain MNC prep with low platelet numbers and the highest possible purity:

Whole blood/buffy coat and bone marrow can be used as a starting material.

1. Dilute 10-18 mL blood/buffy coat with PBS w/ 0.1% BSA + 0.6% Na-citrate or 2 mM EDTA to a total volume of 35 ml at 18-25 degrees C.
2. Add the diluted blood/buffy coat on top of 15 mL of gradient medium (such as Lymphoprep or Ficoll solution).
3 .Centrifuge at 160 x g for 20 min at 20 degrees C. Allow to decelerate without braking.
4. Remove 20 mL of supernatant to eliminate platelets.
5. Centrifuge at 350 x g for 20 min at 20 degrees C. Allow to decelerate without braking.
6 .Recover MNC from the plasma/Lymphoprep solution interface and transfer the cells to a 50 mL tube.
7. Wash MNC once with PBS w/ 0.1% BSA by centrifugation at 400 x g for 8 min at 2-8 degrees C.
8. Wash MNC twice with PBS w/ 0.1% BSA by centrifugation at 225 x g for 8 min at 2-8 degrees C and resuspend the MNC at 1 x 10E8 MNC per milliliter in PBS w/ 0.1% BSA.

Buffy coat, also known as leukocyte concentrate, is the middle fraction of an anti-coagulated blood sample that sits under the plasma and on the top of red blood cells after centrifugation of the sample without using a density gradient reagent such as Ficoll solution. Buffy coat contains both leukocytes and platelets and can be used as a source of this cellular material.

Typically, one milliliter of adult human blood contains:
~5 x 10E9 red blood cells
~7 x 10E6 leukocytes
~3 x 10E8 platelets

In the 7 x 10E6 leukocyte fraction, there are:
4 x 10E5 monocytes
1 x 10E5 NK cells

Lymphocytes:
2 x 10E5 B cells
1 x 10E6 T cells (approx. 70% are CD4+ T cells and 30% are CD8+ T cells)

Granulocytes:
5 x 10E6 neutrophils
2 x 10E5 eosinophils
4 x 10E4 basophils

This will depend on your application. As a guideline, the 4.5 micron beads are best used for cell isolation and activation/expansion. These larger beads have a higher magnetic mobility, they are roughly the same size as mammalian cells, and are less likely to be taken up by the cells. The smaller 1 micron beads and 2.8 micron beads are often used when isolating nucleic acids or proteins, or for immunoprecipitation. In negative cell isolation kits, one micron beads are often used because of their higher binding capacity per milliliter of beads and faster binding kinetics. With negative selection, cells taking up any beads will not be a problem as you want to look at the remaining cell population anyway. The 2.8 micron Dynabeads magnetic beads, coated with secondary antibodies, protein A or protein G, or streptavidin are also used for positive cell isolation with primary antibodies of your own choice, targeting specific cell-surface antigens.

Three different sizes of Dynabeads magnetic beads are available: One micron beads (look for MyOne magnetic beads in the product name), 2.8 micron beads, and 4.5 micron beads. In general, the binding capacity per milliliter of beads and binding kinetics increases as the bead size reduces.

Dynabeads magnetic beads are super-paramagnetic, meaning they only display magnetic characteristics when a magnet is present. As soon as the magnet is removed, the beads handle like a liquid and are easily dispersed in the sample tube. For cell isolation purposes, this has clear advantages as it allows for gentle handing and reduced stress to the cells. Secondly, the beads all have the same size and shape, with rapid liquid-phase reaction kinetics. The smooth surface of the beads results in less non-specific binding. These properties tend to reduce variability and allow you to get more reliable and reproducible results for your purifications and your analyses whether you are looking at cells or any other target molecule (RNA/DNA/proteins/protein complexes/organelles/exosomes etc.)

Here are some suggestions:

- Titrate/optimize the target antibody amount when coating the CELLection Dynabeads magnetic beads.
- If the target cell number is low or the target antigen concentration on the cell surface is low, use the indirect technique.
- Always use >1 x 10E7 beads per milliliter sample (>25 µL).
- Wash whole blood before use.
- To ensure the most efficient cell release, never vortex DNase when resuspending freeze-dried DNAse.
- For cell release, use fresh RPMI/1% FCS pre-warmed to 37 degrees C.
- Check the pH of the RPMI. It should be 7.0-7.4. Higher pH will inhibit DNase activity.
- RPMI should contain sufficient Mg²⁺ for DNase activity.
- After cells are incubated with DNase Releasing Buffer, it is essential that the bead-cell complexes are thoroughly pipetted before the magnetic separation to provide mechanical disruption to the DNA linker. Failure to pipette the cells will affect cell yield

Here are some suggestions:

- Make sure that pH of the RPMI + 1% FBS is not too high: DNase I works best between pH 7.0-7.4 (O₂ exposure of RPMI will result in increased pH and the pH-indicator will turn blue).
- Do not use RPMI + 10% FBS during DNase I treatment. 10% FBS gives a lower cell yield than 1% FBS (might be caused by DNase I inhibitory factors in some batches of FBS).
- Make sure that the buffer contains Mg²⁺/Ca²⁺ required for DNase activity.
- DNase I must be treated gently. Vigorously stirring of the DNase solution can reduce the enzyme activity. Never vortex the DNAse solution.
- When selecting low numbers of cells, we recommend that you pre-coat tubes with RPMI + 10% FBS to reduce cell loss (cells are sticky and will easily attach to the tube wall during selection).
- DNase I has good activity at 20 degrees C, however, we recommend pre-warming the RPMI + 1% FBS to 37 degrees C before starting DNase I treatment because ‘room temperature' varies from lab to lab.
- After cells are incubated with DNase Releasing Buffer it is essential that the bead-cell complexes are thoroughly pipetted before the magnetic separation to provide mechanical disruption to the DNA linker. Failure to pipette the cells will affect cell yield.