Complement system proteins and related proteins including lectin pathway proteins [such as galectin-3 (Boza-Serrano et al., 2022; Wang et al., 2015) and mannan-binding lectin (MBL) (Lanzrein et al., 1998)], as well as the more investigated classical and alternative pathways have exhibited differential expression in PD, AD, and MS (Kodosaki et al., 2024; Dufek et al., 2009; Naskar et al., 2022; Khosousi et al., 2023; Krance et al., 2021). Here, MBL2 is linked to Alzheimer disease.