IL17A and Alzheimer disease: As shown in Figure 6, a–c, 2-month treatments with antibiotics significantly reduced immunoreactive Aβ density from 6.02% ± 0.32% to 4.42% ± 0.64% in the cortex and from 5.67% ± 0.34% to 4.16% ± 0.58% in the hippocampus (t test, p < 0.05) of Il-17a-wildtype AD mice.