While some studies demonstrated increased protein levels of HO-1 in AD lymphocytes [186], others have shown decreased HO-1 mRNA and protein levels in lymphocytes, plasma, choroid plexus, and CSF from early AD and from some amnestic MCI patients [211, 212] and augmented activity of HO-1 suppressor (HOS) in AD plasma [213]. The gene discussed is HMOX1; the disease is Alzheimer disease.