Figure 4.

Delayed proliferation of CD45RA⁺ CCR7⁺ CD8⁺ T cells in response to IL-7 or IL-15. (a, b) Purified cells cultured with 50 ng/ml of IL-7 or IL-15 for 34 days (representative data shown for one experiment of four). Spontaneous apoptosis of cells in medium alone was ≥90% by day 7 (data not shown). (a) Viable cell numbers were determined at different time points by sampling bulk cultures repeatedly (trypan blue exclusion). (b) Proliferation was measured by [³H]-thymidine incorporation at the indicated time points. (c–e) CFSE-labelled cells were cultured as indicated and cell division measured by flow cytometry. (d, e) dotted line day 3, solid line day 13, solid fill day 21.