T cells from DLBCL patients who have received multiple rounds of chemotherapy show loss of CD27 and CD28 expression. Peripheral blood samples from healthy controls, untreated DLBCL patients, and heavily-treated DLBCL patients were examined for the expression of CD27 and CD28 by flow cytometry. (A) Representative flow plots of CD27 and CD28 expression gated on CD3+ cells. (B) Quantification of CD27−CD28− cells from healthy controls (n = 6), untreated DLBCL patients (n = 5), and treated DLBCL patients (n = 12). Horizontal bar shows mean values; vertical “whiskers” show 95% confidence interval. (C) Linear regression showing the correlation between number of total chemotherapy cycles and frequency of CD27−CD28− cells in DLBCL patient samples. Colored symbols and connecting lines indicate paired blood samples taken from DLBCL prior to and following cytotoxic chemotherapy.