Mechanism of CD4 T-cell pool expansion. PBMCs were assayed by flow cytometry. (A) Proportions of CD4 and (B) CD8 T cells expressing the proliferation marker Ki-67. The solid blue line represents median values and the dotted blue lines represent the upper and lower IQRs. Data from each of the 9 patients are included at each time point. rhIL-7 was administered as a series of injections once per week for 3 weeks. Each dotted vertical orange line represents a dose of rhIL-7. (C) Fold change in T-cell receptor excision circle (TREC) content. (D) Fold change in CD31 expression in PBMCs in the weeks after initiation of rhIL-7 therapy. Each patient’s results are depicted by color and symbol as in Figure 2.