Plasma glutamate levels, lymphocyte reactivity and death rate in patients with bronchial carcinoma.

Elevated glutamate concentrations are commonly observed in patients with advanced carcinoma, and glutamate was recently found to inhibit the membrane transport of cystine and to impair the function of macrophages and lymphocytes in vitro. We therefore investigated the possibility that elevated plasma glutamate levels may be quantitatively correlated with reduced lymphocyte reactivity and an impaired host response to the tumor. Here we report the results of a study on patients with bronchial carcinoma, which show that patients with plasma glutamate levels above 120 microM have a lower lymphocyte response to mitogens and a substantially higher death rate than those with glutamate levels below 120 microM. This correlation does not prove a causal role of glutamate, but it confirms predictions from the in vitro laboratory data.