In cohort I, we analysed the correlation between the plasma IgA levels and cognition (assessed by ADAS-Cog, MMSE, and AQT memory tests), inflammation (indicated by CRP levels), BBB permeability (indicated by Q-albumin ratio), and CSF AD biomarkers such as CSF Aβ40, Aβ42, p-tau, and t-tau. Here, CRP is linked to Alzheimer disease.