CD4 and CD8 T-cell subset counts before and after treatment for HD. Shown are the medians and interquartile ranges (error bars) of the absolute counts for the total, memory, and naive CD4 and CD8 subsets in the following groups: healthy controls (n = 34), HD patients before treatment (n = 19), subjects who had been treated for HD within 2.5 years (n = 23), 2.5 to 5 years (n = 10), and more the 5 years (n = 23) before analysis. Naive and memory subsets were determined based on expression of CD62L and CD45RA as shown in Fig 1. Subjects were treated for HD with either radiation alone or combined radiation and chemotherapy. Significant differences between the healthy controls and any of the other groups are shown along the top; significant differences between the HD patients before treatment and the posttreatment HD subjects are shown below this. Note that the control group and posttreatment HD groups were appoximately matched for age; however, five of the treated HD subjects were older than the oldest control individual (60 years). Because older age may have an effect on the representation of T-cell subsets, we also analyzed the data excluding these five older HD patients. The significance of the decrease in the naive CD4 and CD8 T-cell counts, as well as the decrease in the total CD4 T-cell count, was not changed.