Identification of malignant and nonmalignant T-cell clones in patients 4, 8, and 10 using TCR Vβ, CD158k, and cell-surface VIM phenotyping. Molecular characteristics of the T-cell clones are shown on the left, and the results of 2-color flow cytometry analyses are shown on the right. (A) A strongly expanded TCR Vβ7-Jβ1.2 T-cell clone was identified in patient 4, expressing CD158k and displaying heterogeneous labeling with SC5 mAb. A minor CD158k^– population could be recognized within the Vβ7⁺ population (arrowhead). (B) A nonmalignant TCR Vβ17-Jβ2.2 T-cell clone was identified in patient 8, accounting for 10% of gated lymphocytes. Two-color flow cytometry showed that the TCR Vβ17⁺ population displayed heterogeneous expression of cell-surface vimentin (SC5) but was negative for CD158k. (C) A nonmalignant TCR Vβ14-Jβ1.6 T-cell clone was identified in patient 10 during treatment with anti–CD52 mAb (alemtuzumab) that was heavily expanded and did not express CD158k, as seen on the right based on the results of 2-color flow cytometry.