CNS Microvascular Pericytes Express Macrophage-like Function, Cell Surface Integrin αM, and Macrophage Marker ED-2

CNS pericytes are an integral part of the blood–brain barrier (BBB), but their function is not well understood. We questioned whether primary cultured CNS pericytes have immune potential. Primary cultured pericytes exhibit phagocytic activity when exposed to fluorochrome-conjugated polystyrene beads and antibody-coated zymosan. Maximum phagocytic activity occurred by 3 hr. Pericytes were found to express the macrophage markers ED-2 and the integrin subunit CD11b (αM) in culture as well as on isolated microvessels. Pericytes did not express the macrophage marker ED-1. We confirm the heterogeneity of cultured CNS pericytes with regard to expression of α-smooth muscle actin. In conclusion, pericytes express macrophage surface antigens and have the ability to perform at least some immune function. CNS pericytes may therefore have a role in neuroimmune networks at the BBB.