The excitotoxic effect of NMDA on human lymphocyte immune function.

N-Methyl-d-aspartate (NMDA)-activated glutamate receptors are expressed in lymphocytes, but their roles have not yet been defined. We show that incubation of human peripheral blood lymphocytes with NMDA resulted in increased intracellular calcium and reactive oxygen species (ROS) levels through effects on NMDA-activated glutamate receptors. In terms of ROS production, T cells were most affected, followed by NK cells, whereas B cell ROS levels were not increased. In unstimulated T and NK cells, interferon-gamma (IFN-gamma) production was unaffected by NMDA, whereas interleukin-2 stimulation of IFN-gamma production was significantly suppressed by NMDA. Simultaneous incubation of the cells with NMDA and IL-2 resulted in a dramatic increase in the amount of cells expressing the NR1 subunit of the NMDA-activated receptors. We conclude that NMDA-activated glutamate receptor activation, accompanied by the changes in intracellular calcium and ROS levels, may be involved in the modification of immune functions of human T and NK cells.