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

Abstract

Background

Vα24⁺ 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.

Methods

We 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).

Results

The 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.

Discussion

G-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.

• CD1d
• α-galactosylceramide
• granulocyte colony-stimulating factor
• malignant lymphoma
• natural killer T cells