Figure 2.

(A) Kinetics of de novo surface CD4 expression of activated CD8⁺ T cells. CD4-depleted PBMC were obtained from two healthy donors and activated with PHA or SEB. Cells were stained for CD4 and CD8 at various days (from day 0 to day 27) as described in Materials and Methods. Percentages of CD8⁺ T cells expressing the CD4 antigen were determined after analysis of 10,000 events. (B) CD4 mRNA levels before and after CD8⁺ T cell activation. Resting CD4⁺, resting CD8⁺ and SEB activated CD8⁺ T cells from three healthy donors were analyzed for CD4 protein and CD4 mRNA expression. (Top) The CD4/CD8 flow cytometry profiles of one of the donors, which is representative of the two other donors. RNA from each category (resting CD4⁺, resting CD8⁺, and activated CD8⁺) was extracted and subjected to RT-PCR for both CD4 mRNA and G3PDH mRNA expression. For each sample, a minus RT control was included to monitor for possible genomic contamination.