At day 7 after fracture, middle-aged mice (MA, n=6) had significantly higher plasma IL-6 than juvenile mice (Ju, n=6, p<0.01). After rejuvenation of bone marrow, plasma IL-6 in middle-aged mice (Ju:MA, n=6) was significantly lower than in controls (MA:MA, n=7, p=0.014). Plasma IL-6 in juvenile mice with aged marrow (MA:Ju, n=4) was higher than controls (Ju:Ju, n=5), but not significant. TNF-alpha exhibited the same trend (* p>0.05)