DIFFERENTIAL ADHESION OF MACROPHAGES TO WHITE AND GREY-MATTER IN AN IN-VITRO ASSAY

Microglia, the resident macrophages of the brain, are monocytic cells whose phenotype is determined during development by the unique environ ment of the central nervous system (CNS). They are quiescent cells whe n compared with other tissue macrophages, and this downregulation may have important consequences for inflammatory and immune responses in t he brain. In the search for features of the brain environment which mi ght exert an influence on microglial behaviour, we have concentrated o n the possible role of adhesion molecules. We have developed a robust and reproducible in vitro adhesion assay to look at the interaction be tween macrophages and brain tissue. We describe here the characterisat ion of this assay. By injecting agents into the brain in vivo, we were able to study the effect of perturbations in the resident cell popula tion on the adhesion of macrophages to brain tissue in vitro. This pro vided strong evidence that RAW 264 cells adhere to neurones in prefere nce to other CNS cell types in this assay, and this was confirmed by a dhesion assays performed on monolayers of individual cell types. We hy pothesise from these results that macrophages interact with CNS neuron es in vivo via adhesion molecules, enabling them to sense and respond rapidly to pathology in the brain. (C) 1998 Wiley-Liss, Inc.