Relationship of naive CD4 and CD8 counts to age. There is a slight trend to lower numbers of naive CD4 and CD8 cells in older healthy controls (but it is not statistically significant). There is no statistically significant effect of age on the absolute numbers of naive CD4 or CD8 cells in any of the HD-treated populations. While the rate of increase in cell counts during the acute recovery phase may be age-dependent, the equilibrium naive cell counts do not show an age dependence. The far right panel shows naive CD4 and CD8 counts for 11 individuals treated with radiotherapy or radio- plus chemotherapy for NHL; these individuals have a similar long-term loss of naive T-cell counts, suggesting that the treatment, identical to that used for the HL patients, is itself an important contributor to the long-term lack of naive T-cell regeneration.