CD48 expression concentrations were decreased in parallel with ATLL disease aggressiveness. (A) CD48 mRNA expression in CD4 T cells purified from peripheral blood of healthy donors (n = 21), smoldering-type ATLL (n = 4), chronic-type ATLL (n = 20), and acute-type ATLL (n = 26). Data were obtained through a publicly available microarray dataset GSE33615. (B) CD48 mRNA expression in CD4 T cells purified from peripheral blood of chronic-type ATLL (n = 19) and acute-type ATLL (n = 22) from another publicly available microarray dataset GSE1466. (C) Cell surface CD48 expression by flow cytometry on CD3⁺CD4⁺CD25⁺ T cells in healthy donors (n = 3; healthy donor #1, #7, and #8) and acute-type ATLL patients (n = 3; acute-type ATLL #9, #10, and #11). (D) Cell surface CD48 expression using flow cytometry on ATLL cells or normal bystander CD4⁺ T cells in 3 patients with acute ATLL (#9, #10, and #11). Representative dot plots are indicated for the gating strategy for ATLL cells (CD3⁺CD4⁺CD7⁻) or normal bystander CD4⁺ T cells (CD3⁺CD4⁺CD7⁺). Mean fluorescence intensity (MFI) of CD48 was shown on the right side. (E) MFI of CD48 in ATLL cells or normal bystander CD4 T cells from (D) were plotted. (F) CD48 mRNA expression in CD4 T cells purified from peripheral blood of healthy donors (n = 20) and in lymph node biopsy samples of PTCL NOS (n = 144), AITL (n = 127), ALK⁻ ALCL (n = 69), ALK⁺ ALCL (n = 53), and ATLL (n = 16) from a publicly available microarray dataset. (G) Kaplan-Meier curve for overall survival in ALK⁻ ALCL with higher (n = 22) or lower (n = 15) CD48 expression values. The threshold was set as the median value of CD48 expression. P value of the log-rank test statistic is shown. Error bars represent median and 95% CI in (A), (B), and (F), and mean and 95% CI in (C) and (E). ∗P < .05, ∗∗P < .01, ∗∗∗P < .001, Welch 2-sample t-test.