Imaging of Leukocyte-Endothelium Interaction Using In Vivo Confocal Laser Scanning Microscopy during the Early Phase of Experimental Pneumococcal

Confocal laser scanning microscopy (CLSM) was used to investigate dynamic aspects of rho-damine 6G-labeled leukocytes in the pial microcirculation during the early phase of pneumococ-cal meningitis. Closed cranial windows were implanted into anesthetized rats without removing the dura mater. Leukocyte behavior was studied every hour after intracisternal (ic) injection. The number of adherent and extravasated leukocytes was determined during playback of videotaped images. Compared with results in controls, the number of adherent leukocytes increased signifi-cantly (P <.05) within 1 h after ic pneumococcal challenge, followed by a further increase up to 6 h after infection. In untreated infected rats, the number of extravasated leukocytes progressively increased from 3 to 6 h after infection. Leukocyte adherence to microvascular endothelium occurred in pial venules but not in arterioles. Dexamethasone pretreatment significantly (P <.05) attenuated leukocyte adherence and transendothelial passage of leukocytes. Pneumococcal meningitis is a serious disease, with mortal-ity rates still reaching 20%-30 % [1-3]. Much of our present knowledge of the pathophysiology of bacterial meningitis stems from rabbit and rat models. Pathophysiologic mecha-nisms that may lead to brain injury include brain edema an