Nanoparticle-Based Enrichment and Expansion of Antigen-Specific CD8+ T Cells

To isolate antigen-specific CD8-positive T cells, macerate the spleens and lymph nodes from wild-type C57Black/6j mice through a sterile 70-micrometer cell strainer with frequent PBS rinses, and use a no-touch CD8-positive T cell isolation kit, according to the manufacturer's instructions, to eliminate the non-CD8-positive T cells.

After counting, collect the isolated CD8-positive T cells by centrifugation, and resuspend the pellet in 100 microliters of PBS, supplemented with 0.5% bovine serum albumin and 2-millimolar EDTA.

Then, incubate the cells with the nanoparticle artificial antigen-presenting cells such that there are 1 x 10¹¹ peptide-loaded MHC-Ig, per 1 x 10⁶ isolated CD8-positive T cells in a sterile 5-milliliter polystyrene round-bottom tube for 1 hour at 4 degrees Celsius with continual mixing.

At the end of the incubation, wash the nanoparticle cell suspension three times on the magnetic stand as demonstrated, re-suspending the artificial antigen-presenting cells and the enriched CD8-positive T cells in 500 microliters of fresh supplemented medium with 1% T cell growth factor, after the last wash.

For maximum cell recovery, it is critical to leave the particles in cells on the magnetic column for at least 2 minutes, and to aspirate the buffer carefully without disrupting the particles and cells subject to the magnetic field.

After counting, seed 2.5 x 10⁵ enriched CD8-positive T cells and magnetic particle mixture per 160 microliters of supplemented medium plus 1% TCGF in a 96-well U-bottomed plate. On day three, feed the cells with 80 microliters of supplemented medium with 2% T cell growth factor per well, and return the plate to the cell culture incubator for four more days.

On day seven, harvest the stimulated cells into a 5-milliliter round-bottom tube for counting, and collect the cells by centrifugation. Resuspend the pellet in 0.5 milliliters of PBS supplemented with 0.05% sodium azide and 2% fetal bovine serum for counting, and aliquot 5 x 10⁴ to 5 x 10⁵ cells into new 5-milliliter round bottom tubes for antigen-specific staining.

Label the appropriate tubes with biotinylated MHC-Ig and anti-mouse CD8a for 1 hour at 4 degrees Celsius, followed by a centrifuge wash in fresh PBS, to remove any excess biotinylated immunoglobulin. Then, stain the samples with an appropriate streptavidin-conjugated secondary antibody, and an appropriate live/dead fixable dead cell stain for 15 minutes at 4 degrees Celsius, and read the cells on a flow cytometer to determine the specificity and number of the antigen-specific CD8-positive T cells, according to standard protocols.