Figure 2. IL-4 induces T cell proliferation in vivo but not in vitro.

A. CFSE-labeled BALB/c spleen cells were cultured with or without IL-4. Cells were stained for CD8 after 1 or 3 d of culture and analyzed for CFSE fluorescence and forward light scatter. Similar results were obtained when cultures were supplemented daily with IL-4 (not shown).

B. 5.7 × 10⁷ CFSE-labeled BALB/c spleen cells were transferred into recipient BALB/c mice, which were then injected i.p. every other day with vehicle or IL-4C (5 μg IL-4/30 μg anti-mouse IL-4 mAb) in vehicle. Spleen cells from recipient mice sacrificed 1, 2 or 3 d after cell transfer were analyzed for number of CD8⁺ CFSE⁺ cells and CD8⁺ T cell CFSE fluorescence.

C. BALB/c mice were injected i.p. on d 0 and 2 with vehicle or IL-4C as in “B” and twice with BrdU on d 2. Spleen cells obtained on d 3 were stained for CD4, CD8, and BrdU and analyzed for BrdU staining on CD4⁺ and CD8⁺ cells.

D. BALB/c IL-4Rα-deficient mice were injected i.v. with 5.3 × 10⁶ (left panels) or 5.0 × 10⁶ (right panels) CFSE-labeled wild-type BALB/c spleen cells. Recipients were also injected i.p. every other day with vehicle or IL-4C (0.04/0.24 μg (left panels) or 0.2/1.2 μg (right panels)). Spleen cells from recipient mice sacrificed 5 d after cell transfer were stained for CD8 and IL-4Rα and analyzed by flow cytometry for numbers of CD8⁺IL-4Rα⁺ cells and CFSE fluorescence. N = 4–5; * signifies p <.05 compared to cells from vehicle-treated mice.