IFNγ induces NOS2 and TNFα mRNA expression in macrophages from young and aged rats. IFNγR1 (A) protein expression (assessed by western immunoblot) was found to be greater in BMDMs prepared from aged compared with young rats (*
P < 0.05, Student’s t-test; n = 3). IFNγ stimulation (50 ng/ml; 24 h) significantly increased TNFα (B), NOS2 (C), CD40 (D) and MHCII (E) mRNA in BMDMs from young and aged rats (***
P < 0.001; ANOVA). The IFNγ-induced increase in TNFα, CD40 and MHCII mRNA was significantly greater in BMDMs cultured from aged rats compared to cells derived from young rats (++
P < 0.01; +++
P < 0.001; ANOVA). (F, G) BMDMs were treated with IFNγ (50 ng/ml) for 3 and 6 h; following this, TNFα supernatant concentration was measured by ELISA. The IFNγ-induced TNFα release from BMDMs only reached significance in cells from aged rats following 3- and 6-h incubation (*P < 0.05, ANOVA; n = 3). Values are presented as means (±SEM; n = 3) expressed as a ratio to β-actin mRNA or as pg/ml. IFNγ, interferon-γ; IFNγR1, IFNγ receptor; NOS2, nitric oxide synthase; CD40, cluster of differentiation 40; MHCII, major histocampatability complex II; TNFα, tumour necrosis factor-α; RQ, relative quantities.