ICAM1 and early-onset autosomal dominant Alzheimer disease: Large glycoprotein involved in the formation of blood clots. While normally blocked by the blood brain barrier (BBB), infiltration of fibrinogen into the brain, such as in the case of Alzheimer’s disease, has been linked with an exacerbation of vascular damage. Reduced levels of fibrinogen are associated with moderate alcohol consumption, as has been reported for other inflammatory biomarkers (e.g., CRP, ICAM-1)