ABSTRACT
To evaluate the entry of lymphocytes into the brain, we isolated lymphocytes from non-immunized Balb/C mice spleens and activated lymphocytes with anti-CD3 and anti-CD28 antibodies. Activated lymphocytes were labeled with fluorescent CSFE in order to identify their entry into the brain. Nonactivated fresh lymphocytes from spleen were also labeled with CSFE as a control. Before injecting CSFE-labeled lymphocytes into the tail vein, some recipient animals were pretreated with LPS intraperitoneally. Both the resting and activated lymphocytes entered the normal brain although their migration occurred with a low frequency. When the recipient mice were pretreated with LPS intraperitoneally, the number of migration of lymphocytes to the brain was increased, and the ICAM-1 expression was also increased in the brain endothelium. There was no significant difference in the migration into the brain between activated and nonactivated lymphocytes. These results suggested that activation state of lymphocytes, especially, antigen-non specific activation by anti-CD3 and anti-CD28 might not be a critical factor for the migration into the brain, and but the endothelial ICAM-1 expression faciliated the efficient transendothelial migration into the brain.