IBN 98-06128 HUDSON The blood-brain barrier (BBB) forms a unique boundary between the circulating blood and the tissue of the brain and spinal cord. Normally the barrier prevents the entry of most immune cells (cells participating on the body's immune response to foreign pathogens), bacteria, viruses, antibiotics, and chemotherapy drugs into the nervous system. The BBB is formed by "endothelial" cells lining the capillaries that exhibit "tight junctions" between adjacent cells. The presence of these tight junctions, which can be recognized by their special dense appearance in electron micrographs, stands in contrast to the situation for endothelial cells of other organs. The formation of the tight junctions is induced by a certain type of cell from the nervous system, termed an "astrocyte." Astrocytes have processes which make contact with the endothelial cells. The role of astrocytes and other "glial" cells (cells closely associated with nerve cells) such as microglia in influencing additional BBB functions is not known. Certain immune cells are capable of adhering and penetrating the BBB, surveying the nervous tissue for antigen, and continuing to the lymphoid tissues for immunity functions. What is not clear, however, is the mechanism for selecting which immune cells penetrate the BBB. Experiments in this project are designed to determine if astrocytes and microglia, stimulated by factors found in circulation, can alter the ability of immune cells to adhere to and penetrate the endothelial cells of the brain. This will primarily be accomplished using cell culture methods in various combinations of endothelial cells, astrocytes, and microglia, stimulated and unstimulated. Immune cells will be applied to the combinations of cells and the ability of immune cells to penetrate the cell layers will be determined using staining techniques and a special microscope that allows the cell layers to be visualized in 3 dimensions. Because adherence and trafficking of i mmune cells in non-nervous tissue is controlled by activation of endothelial cells with increased expression of adhesion molecules, it is possible that astrocytes and/or microglia influence expression of adhesion molecules in brain endothelium through secretion of "cytokines". The presence or absence of adhesion molecules will be detected through staining techniques specific to each. Results of this project will expand understanding of BBB function and immunity in the nervous system of mammals. This POWRE award will promote the further development of Dr. Hudson's research career in this important area.
