VCAM1 and Dilatation of the cerebral artery: The interplay of various factors, including macrophages, T-lymphocytes, IgG, and IgM as well as complement and vascular cell adhesion molecule 1 (VCAM-1) were found in aneurysm walls but not in control vessel walls and is implicated in both extracranial and intracranial aneurysm formation and growth (3); the role of various inflammatory factors was again demonstrated in 2011 when animal models revealed T-cell infiltration, immunoglobulin and complement deposition and activation, and apoptosis within the walls of cerebral aneurysms (4).