IL6 and infection: Serum concentrations of IL-6 and KC 24 hours p.i. were significantly lower in aged mice compared to young mice reflecting a reduced systemic inflammatory response in aged mice during the acute phase of infection [IL-6: 162 (94/532) pg/ml versus 428 (283/792) pg/ml, p = 0.007; Figure 3A; KC: 714 (315/1399) pg/ml versus 1726 (929/3390) pg/ml, p = 0.002; Figure 3B].