types, including blood lymphocytes, lung macrophages, and multiple hematopoietic precursors in bone marrow cells [40, 42, 47, 48] . Both ketamine and the chemically unrelated anticonvulsant dizocilpine (MK-801) are noncompetitive antagonists of the NMDA receptor, one of the three known glutamate receptors [32, 33, 47] . APV is a competitive inhibitor of the classical NMDA receptor and acts on the NR2 component of the receptor (30, 33) . We found that MK-801 and APV also inhibited macrophage TNF secretion in response to antibiotictreated MW2 or LAC cells. The magnitude of the inhibition by MK-801 (approximately 30%) and APV (25-35%) was comparable to that observed with ketamine (18-34%), and combinations of MK-801 and ketamine or of APV and ketamine did not exhibit additive or synergistic inhibition of TNF secretion. Furthermore, adding NMDA led to augmented macrophage TNF secretion in response to antibiotic-treated CA-MRSA bacteria, and the NMDA receptor antagonist, APV, blocked this effect. The suppression of TNF induced by ketamine was observed across a range of concentrations and throughout the incubation period.