TABLE I. Ligation of CD40 by cross-linking antibodies against either CD40 or human recombinant CD40L stimulates the production of NO in IFN-γ-treated mouse primary microglia and macrophages.

Mouse primary microglia and peritoneal macrophages were cultured for 24 h with IFN-γ (25 units/ml) and different concentrations of either cross-linking antibodies against CD40 or human recombinant CD40L under serum-free conditions and nitrite concentration in the supernatants was measured as described under “Materials and Methods.” Data are mean ± S.D. of three different experiments. ND, not determined.

Treatments	Nitrite
	Microglia	Macrophages
	μg/mg protein/24 h
Control	11.7 ± 1.5	12.5 ± 1.6
IFN-γ alone	146.8 ± 16	176.5 ± 21.5
Anti-CD40 (2 μg/ml) alone	12.9 ± 1.1	14.6 ± 1.2
IFN-γ + anti-CD40 (1 μg/ml)	321 ± 36	348 ± 29
IFN-γ + anti-CD40 (2 μg/ml)	412 ± 31	482 ± 55
CD40L (2 μg/ml) alone	ND	15.1 ± 1.9
IFN-γ + CD40L (1 μg/ml)	ND	312 ± 23
IFN-γ + CD40L (2 μg/ml)	ND	407 ± 34