ADHESION PROTEINS ON HUMAN MICROGLIAL CELLS AND MODULATION OF THEIR EXPRESSION BY IL1-ALPHA AND TNF-ALPHA

Expression of adhesion proteins on human microglial cells was studied by immunocytochemistry. Both microglial cells and peripheral blood monocytes expressed beta2 integrins and molecules of the immunoglobulin superfamily at similar levels whereas the expression of the beta1 integrins (alpha2-VLA (very late antigen), alpha4-VLA, alpha5-VLA, alpha6-VLA) was higher on microglial cells than on monocytes. Stimulation of microglial cells with interleukin-1alpha and tumour necrosis factor-alpha, the main cytokines detected in HIV1-infected central nervous system (CNS), increased the microglial expression of alpha1-VLA, intercellular adhesion molecule-1, vascular cell adhesion molecule-1 and beta2-LFA-1 (leukocyte-function-associated molecule-1) but not of alpha(L)-LFA-1. Such an induction of adhesion molecules could facilitate penetration of HIV1-infected monocytes into brain parenchyma and their adhesion to CNS cells, and could maintain a chronic inflammation during human immunodeficiency virus-1 (HIV1) encephalopathy.