Characterization of CD28 isoform proteins in transfected Jurkat T cells.

(A) Distribution of CD28 isoforms in transfected Jurkat T cells. The cDNAs encoding CD28 and CD28i were subcloned into pEGFP to generate C-terminal fusions of CD28 and CD28i with EGFP. Jurkat T cells were transfected with pEGFP or those pEGFP-based plasmids, and cells were monitored 12 hours later by laser confocal microscope. Original magnification × 400. (B) Detection of HA-tagged CD28i on the Jurkat T cell transfectant by cell-surface staining. Jurkat T cells were transfected with the expression vector harboring HA-tagged CD28i. The stable transfectant was stained with rabbit anti-HA Ab and FITC–goat anti–rabbit IgG Ab, then subjected to analysis with flow cytometry. The control was stained with FITC–goat anti–rabbit IgG Ab alone.