Intercellular adhesion molecule-1 (ICAM-1) is a glycoprotein expressed on endothelial cells that facilitates leukocyte adhesion. To test the hypothesis that reduction of leukocytes in an ischemic lesion reduces ischemic brain damage, we measured the effect of administration of an anti-ICAM-1 monoclonal antibody on ischemic brain damage after transient middle cerebral artery occlusion in the rat. ICAM-1 expression increased in the ischemic lesion, and the lesion volume was significantly reduced by 41% in the anti-ICAM-1 antibody group compared with the control group (p < 0.05). Numbers of polymorphonuclear leukocytes (PMNs) were significantly reduced in the cortices of the anti-ICAM-1 antibody group compared with the control animals (p < 0.05). Our data indicate that administration of anti-ICAM-1 antibody results in a significant reduction of ischemic brain damage concomitant with a reduction of PMNs in the lesion after transient focal cerebral ischemia in the rat.

We investigated the role of reactive oxygen metabolites (ROMs) as potential mediators of tumor necrosis factor-alpha (TNF-alpha)-stimulated neutrophil adhesion to rat mesenteric venules in vivo, using intravital microscopy and fixed whole mount preparations of mesentery. Intraperitoneal injection of TNF-alpha significantly increased leukocyte rolling, adhesion, and emigration in a dose- and time-dependent manner. Leukocyte adhesion and emigration, but not rolling, were significantly attenuated by prior intravenous administration of monoclonal anti-intercellular adhesion molecule-1 (ICAM-1). Rolling leukocyte flux was significantly attenuated by intravenous preadministration of superoxide dismutase (SOD), catalase, or both. Only catalase or SOD plus catalase significantly inhibited leukocyte adhesion. Catalase alone inhibited emigration. Moreover, postadhesive treatment with catalase but not SOD, 4 h after TNF-alpha administration reduced the flux of rolling (but not adherent) leukocytes that had previously increased in response to TNF-alpha. Intragastric allopurinol (50 mg/kg at 3 and 18 h before TNF-alpha administration) or 3 wk of a tungsten-enriched diet substantially inhibited xanthine oxidase activity but had no significant effects on the above parameters of neutrophil dynamics. In parallel experiments using fixed whole mount preparations of the mesoappendix stained specifically for neutrophil esterase, neutrophil adhesion 2 h after TNF-alpha administration was also inhibited by continuous intravenous administration of catalase but not by SOD, intragastric allopurinol, or tungsten diet. These findings suggest that ROMs, apparently not from xanthine oxidase, are important mediators of TNF-alpha-induced upregulation of neutrophil adhesion in rat mesenteric venules.

Although it has been suggested that LFA-1 is one of the important molecules mediating interaction between lymphocytes and high endothelial (HE) cells, the implication was based on the observation that lymphocyte binding to high endothelial venules in frozen lymph node sections was partially inhibited by anti-LFA-1 monoclonal antibody at 4 degrees C. However, it has previously been unequivocally demonstrated that LFA-1 molecule is unable to function at this low temperature. To assess the actual involvement of LFA-1 in lymphocyte-HE cell interaction at body temperature, we examined effects of newly developed anti-rat LFA-1 and anti-rat ICAM-1 monoclonal antibody on binding of resting or activated lymphocytes to a rat HE cell line at 37 degrees C. We found that (a) LFA-1/ICAM-1-independent pathway was predominant in the interaction between resting lymphocytes and HE cells, indicating that LFA-1 functions little, if any, in the interaction and (b) lymphocyte triggering through CD3 significantly increased binding inducing a LFA-1/ICAM-1-dependent pathway, whereas phorbol 12-myristate 13-acetate stimulation also enhanced lymphocyte binding but inducing a LFA-1-dependent/ICAM-1-independent pathway. In both cases no apparent alteration in LFA-1 expression was observed, suggesting that the increase in lymphocyte adhesion was not due to quantitative but a qualitative change induced in LFA-1 molecule upon lymphocyte stimulation. These findings suggest that LFA-1 is normally inert but can be "switched" upon lymphocyte stimulation to participate in lymphocyte-HE cell interaction, and that the LFA-1's ligand specificity can be differentially regulated at the lymphocyte-HE venule interface.

The surface phenotype of cells in peripheral lymph collected from afferent lymphatics leading to the popliteal lymph node of sheep was determined using a panel of monoclonal antibodies (mAbs). The majority of lymphocytes (83.5%) expressed the sheep pan-T cell antigen and only 13.3% bore surface immunoglobulin molecules. All peripheral T cell subsets occurring in sheep were detected; 50.2% of lymphocytes were positive for mAb SBU-T4 (T helper), 7.3% were positive for mAb ST-8 (T cytotoxic), and 8.4 and 43.0% expressed T subset markers recognized by mAbs 197 and T-80, respectively. Major histocompatibility complex (MHC) class I antigens were detected on 71.1% of lymphocytes and MHC class II antigens on 21.8%. The macrophage/veiled cells found in peripheral lymph did not express lymphocyte subset markers but were positive for MHC class I and II antigens, the sheep homologue of T6 antigen, leukocyte common antigen and mAb 175 (myeloid/erythroid). Macrophage-like cells occurring in the epidermis of skin taken from the lower hindleg gave positive staining reactions to the same mAbs which stained the macrophage/veiled cells in peripheral lymph. These results illustrate differences between the migration of lymphocyte subsets through nonlymphoid as compared to lymphoid tissues and point to a possible developmental or migratory relationship between the macrophage-like cells in skin and those in afferent popliteal lymph.