IL18 and Alzheimer disease: By calculating free IL-18 (Fig. 2, lower panel), subjects with MCI (161.6 ± 60.2 pg/ml) showed a significant increase in the levels of the free cytokine compared to NHS (111.0 ± 45.1 pg/ml, p < 0.001), SMC (124 ± 45.8 pg/ml, p = 0.012), and AD (95.4 ± 123.4 pg/ml, p = 0.049).