FIGURE 6.

Naive CD4 T cells from Abcg1^−/− mice are hyperproliferative to TCR stimulation. Naive CD4 T cells were purified from spleen. A, Cells (n = 4) were stimulated with plate-bound αCD3 (1 μg/ml), soluble αCD28 (1 μg/ml), and IL-2 (10 U/ml). ³H thymidine was added to cultures after a 48-h stimulation and harvested after 18 h. B, CFSE-labeled cells (n = 4) were stimulated with 1 μg/ml plate-bound αCD3 and 1 μg/ml αCD28, and CFSE dilution was measured after 72 h. C, Cells (n = 3) were stimulated with 1 μg/ml plate-bound αCD3 and 1 μg/ml αCD28 and stained with propidium iodide after 48 h to determine the cell cycle. D, Cells (n = 4) were stimulated with 0.1–10 μg/ml plate-bound αCD3 and 1 μg/ml soluble αCD28, and ³H thymidine incorporation was measured. Graph represents ³H thymidine incorporation (inset). Nonlinear curve regression was used to fit the data to sigmoidal curves and calculate EC₅₀. E, CFSE-labeled cells (n = 6) were stimulated with 5 ng/ml PMA and 100 ng/ml ionomycin, and CFSE dilution was measured after 72 h. F, Cells (n = 4) were stimulated with PMA and ionomycin (iono), and ³H thymidine incorporation was measured. *p < 0.05; **p < 0.01; ***p < 0.0001.