Reactivity of circulating CD4⁺ T cells of patients with indolent B-cell malignancies to in vitro stimulation. MFI indicates mean fluorescence intensity. FL/eMZL, n = 13; CLL, n = 8 patients. (A) Kinetics of activation marker expression, viability, and cell cycle of isolated CD4⁺ T cells after in vitro stimulation with anti-CD3 and anti-CD28. Results from one representative of a series of pilot experiments with T cells from healthy donors. FCM indicates flow cytometry; GEP, gene expression profiling; and Thy, thymidine. (B) Expression of activation markers in total and naive (CD45RA⁺) subsets of CD4⁺ T cells from nonleukemic lymphoma and CLL patients compared with healthy donors 39 hours after stimulation. (C) Proliferative response as determined by thymidine incorporation between 48 and 64 hours (left panel) and viability at 40 hours after stimulation as determined by annexin V staining and flow cytometry. Horizontal bars, boxes, and whiskers represent median, 25%/75% quartiles, and range, respectively.