CD8⁺T-cell proliferation is linked to extent of B-cell expansion in AIM. (A) (left panel) Acute EBV tonsil contains EBER⁺ cells in the IFZ (original magnification × 100). (middle and right panels) Ki-67 staining in control and AIM tonsil sections, respectively (original magnifications × 100). Proliferative activity is low in the interfollicular zones and the follicular MZ compared with GCs in control (middle panel), whereas AIM tonsils show high proliferative activity in the expanded interfollicular T-cell zones (right panel). (B) Proliferation index (percentage of Ki-67⁺) of interfollicular T cells is markedly increased in AIM patients compared with controls (Mann-Whitney U test; P < .0001). (C) Ratio of CD4- to CD8-expressing cells was counted exclusively in the interfollicular zones. (D) Linear regression analysis showed that the increase in proliferative activity correlated with the number of EBV-infected cells, expressed as number of EBER⁺ cells per 10 000 lymphocytes (r = 0.57).