The CD4/CD8 ratio is decreased in thymoma.

(A) Bar graph shows the mean percentages of mature CD4⁺(■) and CD8⁺ (░) thymocytes in residual thymus (resT; n = 9), thymus with thymic follicular hyperplasia (TFH; n = 11), and thymoma (Tm; n = 19), as determined by FACS-based analyses gated on CD3⁺ T cells. Error bars indicate the SE. The percentage of mature CD8⁺ T cells is similar among nonneoplastic thymuses (resT, TFH) and thymomas (P = .9). The percentage of CD4⁺ T cells is similar between resT and TFH (P = .9), but significantly lower between nonneoplastic thymuses (resT, TFH) and thymomas (P = .0001). (B) Diagram compares CD4/CD8 ratios among CD45RA⁺ T cells in individual cases. T cells were derived from thymus and blood (PBL) of TFH patients (n = 7) and from thymoma (Tm) and PBL of thymoma patients (n = 9). The proportion of CD4/CD8 CD45RA⁺ T cells was calculated for thymocytes and PBL from each patient, using FACS-based analyses gated on CD3⁺ T cells. Each asterisk represents the mean ratio among either TFH or Tm and corresponding PBL, respectively. CD4/CD8 ratios of thymoma-derived CD45RA⁺ T cells were significantly decreased (P = .013) when compared with those of thymocytes from patients with TFH. CD4/CD8 ratios among CD45RA⁺ PBL were also decreased in thymoma patients compared with TFH patients, although this represented only a trend (P = .08). In patients with thymoma, CD4/CD8 ratios were elevated (P = .07) among circulating CD45RA⁺ T cells compared with thymocytes, whereas CD4/CD8 ratios were almost identical among CD45RA⁺ T cells in the periphery and thymus of TFH patients (P = .83). ▵, Tm/MG+; ▴, Tm/MG −; ♦, TFH/MG+.