Insufficient ex vivo expansion of Vα24+ natural killer T cells in malignant lymphoma patients related to the suppressed expression of CD1d molecules on CD14+ cells

BackgroundVα24+ natural killer T (NKT) cell is a human counterpart of mice Vα14+ NKT cell that has a regulatory role for innate and acquired potential antitumor activity. The efficient expansion of NKT cells is an obstacle to the clinical application of Vα24+ NKT cells for immunotherapy.MethodsWe used mononuclear cells (MNC) obtained from the peripheral blood (PB) of normal healthy donor (HD) and malignant lymphoma (ML) patients before and after granulocyte colony-stimulating factor (G-CSF) treatment. MNC were cultured for 12 days with α-galactosylceramide (100 ng/mL) and interleukin-2 (IL-2; 100 U/mL).ResultsThe fold expansion of Vα24+ NKT cells was higher in HD than in ML patients (208 versus 0.00), despite comparable numbers of Vα24+ NKT cells before culture. G-CSF administration enhanced the predominance of Vα24+ NKT cell fold expansion in HD compared with ML patients (1935 versus 1.95). After treatment with G-CSF, the expression of CD1d molecules was up-regulated in CD14+ cells from HD but not ML patients. The fold expansion of Vα24+ NKT cells and CD1d expression on CD14+ cells was strongly correlated in both HD and ML patients (r2 = 0.84). However, replacement of a patient's CD14+ cells with HD cells did not increase the efficacy of Vα24+ NKT cell expansion.DiscussionG-CSF-mobilized PB from ML patients has inhibitory characteristics for Vα24+ NKT cell expansion as a result of both monocytes and Vα24+ NKT cells. Multiple procedures would be needed for the expansion of patients’ Vα24+ NKT cells.