Figure 4.

Fold increase or decrease in proliferation after depletion of CD25⁺ cells from PBMCs purified from blood before and 1 wk after in vivo challenge with cow's milk. Predepletion level (see Fig. 3 A) is set to 1 (dotted line). The depleted and nondepleted PBMC samples were tested for proliferative activity, unstimulated and after in vitro stimulation with bovine β-LG or the mitogen PHA. Radioactive thymidine (³H-Tdr) was added 6 d after addition of antigens to the cell cultures. The cells were harvested 12–16 h later. Incorporation of ³H-Tdr was determined in a β-counter. Student's t test was used for statistical analysis. For comparison with absolute proliferative activity (cpm values) of in vitro–stimulated PBMCs collected from allergic and tolerant children before and after in vivo challenge, see Fig 3 A.