Peripheral Blood Mononuclear Cells (PBMC) are labeled with BD IMag™ anti-human CD4 Particles - DM according to the following Protocol. This labeled cell suspension is then placed within the magnetic field of the BD IMag™ Cell Separation Magnet (Cat. No. 552311). Labeled cells migrate toward the magnetic (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.
MAGNETIC LABELING PROTOCOL
1. Prepare PBMC from anti-coagulated human (or rhesus macaque) blood, preferably by density gradient centrifugation using Ficoll-Paque™.*
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. Count cells, wash them with an excess volume of 1X BD IMag™ buffer, and carefully aspirate all the supernatant.
4. Vortex the BD IMag™ anti-human CD4 Particles - DM thoroughly, and add 50 µl of particles for every 10^7 total cells.†
5. MIX THOROUGHLY. Incubate at room temperature for 30 minutes. ‡
6. Bring the BD IMag™-particle labeling volume up to 1 - 8 x 10^7 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 to the same volume as in Step 6. 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).
* Hints for successful cell preparation:
-Draw the blood into a tube containing EDTA.
-Remove the platelet rich plasma by centrifuging once at 220-240 × g.
-Wash 2-3 times in PBS after the density gradient separation.
-Remove clumps of cells and/or debris by passing the suspension through a 70-µm nylon cell strainer.
† The BD IMag™ particles may need to be titrated to optimize the separation of rhesus macaque leukocytes.
‡ Avoid nonspecific labeling by working quickly and adhering to the recommended incubation times.