Fig 1. Id1 expression promotes anti-CD3-induced activation of naïve CD4-Id1^tg CD4⁺ T cells.

Naïve CD4⁺ T cells from wild type (WT) or CD4-Id1^tg (TG) mice were stimulated with anti-CD3 (1.0 µg/ml) with or without anti-CD28 (2.0 µg/ml). (A) BrdU incorporation. Cells were cultured for 3 days and BrdU was added to the culture in the last hour. Representative histograms are shown (left) and the results from 4 independent experiments are presented as mean±SD (right). (B) ³H-TdR uptake. Cells were cultured for 48 hours and ³H-TdR was added 12 hours before harvest. Results from three independent experiments are presented as mean±SEM. (C) CD44 and CD25 expression was compared between anti-CD3 or anti-CD3/CD28 stimulated WT (shaded) and TG (line) CD4⁺ T cells. Results from one representative experiment out of the three are shown. ***p<0.001.