Chemotaxis of CD8⁺ cells.

(A) IL-16–induced migration of costimulated CD8⁺ T cells. Purified CD8⁺ T cells were costimulated for 3 days. Cells were removed from culture and CD4 expression was verified (46% of cells were CD4⁺CD8⁺). Cells were then labeled with Calcein-AM, placed on 96-well chemotaxis chambers, and allowed to migrate in response to the indicated concentrations of IL-16 or SDF1α (250 ng/mL). Results are the percentage of cells migrating compared with medium-only controls (set at 100% migration). Anti-CD4 mAb (OKT4) was added to the lower chamber with the indicated samples. Asterisks indicate samples with results significantly different from those for medium-only controls (P < .05). (B) Migration of unstimulated and PHA-stimulated CD8⁺ T cells. Purified CD8⁺ T cells were left unstimulated or stimulated with PHA for 3 days. Cells were then removed from culture and CD4 expression was examined (≤ 1% of unstimulated cells or PHA-stimulated cells expressed CD4). Subsequently, cells were labeled with Calcein-AM, placed on 96-well chemotaxis chambers, and allowed to migrate in response to IL-16 (200 ng/mL) or SDF1α (250 ng/mL). Results are the percentage of cells migrating compared with unstimulated, medium-only controls (set at 100% migration). Asterisks indicate samples with results significantly different from those for medium-only controls (P ≤ .05). (C) Intensity of CD4 expression on migrating cells. Purified CD8⁺ T cells were costimulated for 3 days, placed on 96-well chemotaxis chambers, and allowed to migrate in response to IL-16 (200 ng/mL) or SDF1α (250 ng/mL). After 2 hours of incubation, cells that had migrated to the lower chamber were pooled, enumerated, stained for CD4 (allophycocyanin) and CD8 (ECD), and analyzed by flow cytometry. The graph shows the mean fluorescence intensity of CD4 expression on cells that migrated.