ADSL and bacterial meningitis: Clinically, the levels of the AMPs LL-37 and defensins increase in the cerebrospinal fluid (CSF) in response to a bacterial meningitis challenge, and the CSF of patients with bacterial meningitis has antimicrobial activities against both Gram-positive and -negative bacteria (Maffei et al., 1999; Brandenburg et al., 2008), suggesting AMPs may directly contribute to the killing of pathogens in the nervous system.