Central nervous system perivascular cells are immunoregulatory cells that connect the CNS with the peripheral immune system

Perivascular cells are a heterogeneous population found in the central nerv ous system (CNS) and the peripheral nervous system (PNS). Several terms are used for these cells, including perivascular cells, perivascular macrophag es, perivascular microglia, fluorescent granular perithelial cells TGP), or Mato cells. Different terminology used may reflect subpopulations of periv ascular cells within different anatomic regions and experimental paradigms, neuropathological conditions, and species studied. Different terminology a lso points to the lack of clear consensus of what cells are perivascular ce lls in different disease states and models, especially with breakdown of th e blood-brain barrier (BBB). Despite this, there is consensus that perivasc ular cells, although a minor component of the CNS, are important immunoregu latory cells. Perivascular cells are bone marrow derived, continuously turn over in the CNS, and are found adjacent to CNS vessels. Thus, they are pot ential sensors of CNS and peripheral immune system perturbations; are activ ated in models of CNS inflammation, autoimmune disease, neuronal injury and death; and are implicated as phagocytic and pinocytotic cells in models of stroke and hypertension. Recent evidence from our laboratory implicate per ivascular cells as primary targets of human immunodeficiency virus (HIV) an d simian immunodeficiency virus (SIV) infection in the CNS of humans and ma caques. This article reviews current knowledge of perivascular cells, inclu ding anatomic location and nomenclature and putative immunoregulatory roles , and discusses new data on the infection of these cells by SIV, their accu mulation after SIV infection, and a possible role of the immune system in S IV encephalitis. (C) 2001 Wiley-Liss, Inc.