CD161^hi cells in UCB and G-CSF–mobilized leukapheresis products differ in frequency and in regulation of response to TCR signaling. (A) Percentages of CD161^hi T cells in CD8α⁺ T cells in adult blood (n = 57), G-CSF–mobilized adult leukapheresis products (n = 5) and UCB units (n = 5) were evaluated by flow cytometry. Data represent the mean ± SE. (B) Immunomagnetically selected CD8α⁺ T cells from G-CSF–mobilized adult leukapheresis products (n = 5) and UCB units (n = 5) were stimulated with PMA/ionomycin for 5 hours followed by surface and intracellular labeling to identify IL-17 secreting CD161^hi cells. (C) CD161^hiCD8α⁺ T cells were isolated from G-CSF–mobilized leukapheresis products (n = 3) and UCB units (n = 4) and stimulated with αCD3 in the absence of costimulation followed by assessment of tritiated thymidine incorporation after 72 hours. Proliferation of CD161^hi cells from G-CSF–mobilized leukapheresis was restored in the presence of αCD28 costimulation (data not shown). Data represent the mean ± SE.