Splenic macrophages from tc-ptp^-/- mice display an inflammatory phenotype as shown by increased iNOS and NO in response to LPS. (A) The iNOS mRNA levels in spleen cells from 2-week-old tc-ptp^-/- (▪) mice and tc-ptp^+/+ (□) after a stimulation with 100 U/mL IFN-γ and 10 ng/mL LPS for 4 hours. Expression level in naive cells was set as one. Bars represent the mean values ± SE from 5 mice. Statistical significance was determined by a 2-tailed unpaired Student t test. ^*P < .05 tc-ptp^-/- compared with tc-ptp+/+. (B) NO production as measured by nitrite concentrations in the supernatants from spleen cells from 14-day-old (top) and 27-day-old (bottom) tc-ptp^-/- (•) and tc-ptp^+/+ (○) mice cultured with different concentrations of LPS. Five separate experiments were performed and all gave similar results. The results shown are from one representative experiment. (C) NO production as measured by nitrite concentrations in the supernatants from spleen-derived macrophages grown from 19-day-old tc-ptp^-/- (▪), tc-ptp^+/- (•), and tc-ptp^+/+ (○) mice and stimulated with different concentrations of LPS. Three separate experiments were performed and all gave similar results. The results shown are from one representative experiment. The error bars represent the SE from triplicate cultures.