Correlation between the signal and EVs. Three sera from patients with EBV infection (◆◇, ●○, ▲△)were diluted with EV-free NHS (solid lines) or reaction buffer (dotted lines) and subjected to AlphaLISA assay for CD3+CD4+ EVs (a), CD3+CD8+ EVs (b), and CD3+HLA-DR+ EVs (c). The correlation coefficients (r) between alpha signal and serum volume in CD3+CD4+ EV, CD3+CD8+ EV, and CD3+HLA-DR+ EV assay ranged from 0.997 to 1.000 when diluted with EV-free NHS, while they ranged from 0.976 to 0.999 when diluted with reaction buffer. EVs were isolated from nine human sera using a commercial isolation kit, suspended to their original volume with EV-free NHS, and their CD3+CD4+ EVs (d), CD3+CD8+ EVs (e), and CD3+HLA-DR+ EVs (f) were measured together with original sera. The correlation coefficients (r) of nine sera between before and after isolation were 0.997, 0.996, and 0.998 for CD3+CD4+ EVs, CD3+CD8+ EVs, and CD3+HLA-DR+ EVs, respectively. Data are presented as the mean ± SD (n = 2).