Peripheral blood mononuclear cells (PBMC) are labeled with BD IMag™ anti-human CD19 Particles - DM according to the following protocol. This labeled cell suspension is then placed within the magnetic field of the Cell Separation Magnet. Labeled cells migrate toward the magnet (positive fraction), leaving the unlabeled cells in suspension so they can be drawn off (negative fraction). The tube is then removed from the magnetic field for resuspension of the positive fraction. The separation is repeated twice to increase the purity of the positive fraction. The magnetic separation steps are diagrammed in the Separation Flow Chart. After the positive fraction is washed, the small size of the magnetic particles allows the positive fraction to be further evaluated in downstream applications such as flow cytometry system.
MAGNETIC LABELING PROTOCOL
1. Prepare PBMC from anti-coagulated human blood, preferably by density gradient centrifugation using Ficoll-Paque.™ Remove clumps of cells and/or debris by passing the suspension through a 70-⎧m nylon cell strainer.
2. Dilute BD IMag™ Buffer (10X) (Cat. No. 552362) 1:10 with sterile distilled water or prepare 1X BD IMag™ buffer by supplementing Phosphate Buffered Saline with 0.5% BSA, 2 mM EDTA, and 0.09% sodium azide). Store at 4°C.
3. Wash cells with an excess volume of 1X BD IMag™ buffer, and carefully aspirate all the supernatant.
4. Vortex the BD IMag™ anti-human CD19 Particles - DM thoroughly, and add 50 µl of particles for every 10e7 total cells.
5. MIX THOROUGHLY. Incubate at room temperature for 30 minutes.
6. Bring the BD IMag™-particle labeling volume up to a concentration of 1 - 8 x 107 cells/ml with 1X BD IMag™ buffer, and immediately place the tube on the Cell Separation Magnet. Incubate for 8 - 10 minutes.
7. With the tube on the Cell Separation Magnet, carefully aspirate off the supernatant. This supernatant contains the negative fraction.
8. Remove the tube from the Cell Separation Magnet, and add 1 ml of 1X BD IMag™ buffer. Gently resuspend cells by pipetting up and down, and return the tube to the Cell Separation Magnet for another 2 - 4 minutes.
9. With the tube on the Cell Separation Magnet, carefully aspirate off the supernatant and discard.
10. Repeat Steps 8 and 9.
11. After the final wash step, resuspend the positive fraction in an appropriate buffer or media, and proceed with desired downstream application(s).
NOTES:
*A more detailed protocol for the magnetic cell separation appears on the Technical Data Sheet accompanying the Cell Separation Magnet. The concentration of BD IMag™ anti-human CD19 Particles - DM suggested in the protocol has been optimized for the purification of CD19-positive B lymphocytes from human peripheral blood. When labeling target cell populations present at lower frequencies, fewer BD IMag™ particles can be used. Conversely, when labeling target cell populations that are present at higher frequencies, more particles should be used. To determine the optimal concentration of the BD IMag™ anti-human CD19 Particles - DM for a particular application, a titration in two-fold increments is recommended.
*Avoid nonspecific labeling by working quickly and keeping incubation times to a minimum.
