POSTISCHEMIC TREATMENT (2-4 H) WITH ANTI-CD11B AND ANTI-CD18 MONOCLONAL-ANTIBODIES ARE NEUROPROTECTIVE AFTER TRANSIENT(2 H) FOCAL CEREBRAL-ISCHEMIA IN THE RAT

We investigated the effects of F(ab')(2) fragments of anti-CD11b and anti-CD18 monoclonal antibodies on ischemic cell damage in the rat when administered upon reperfusion and at 2 h of reperfusion after transient (2 h) middle cerebral artery (MCA) occlusion. 2 h of MCA occlusion was induced by intraluminal insertion of a monofilament. The following groups of animals were investigated. Anti-CD11b groups (n = 15): an intact anti-CD11b antibody (1B6c) and an anti-CD11b F(ab')(2) fragment of 1B6c were infused upon reperfusion (4 mg/kg i.v.). Anti-CD18 group (n = 8): an anti-CD18 F(ab')(2) fragment of CL26 was infused upon reperfusion (2 mg/kg i.v.), and at 22 h of reperfusion (1 mg/kg i.v.). Anti-CD11b delayed group (n = 9): an anti-CD11b F(ab')(2) fragment of 1B6c was infused at 2 h of reperfusion (4 mg/kg i.v.), and at 22 h after reperfusion (2 mg/kg i.v.). Control groups (n = 18): an isotype-matched control antibody (mouse IgG(1)) was administered: (a) upon reperfusion (n = 13), and (b) at 2 h and 22 h of reperfusion (n = 5). Rats were sacrificed at 7 days of reperfusion. In a separate population of rats subjected to 2 h of MCA occlusion (n = 9), brain myeloperoxidase (MPO) activity was measured at 46 h of reperfusion. The vehicle groups had infarct volumes of 35.21+/-2.82% to 41.39+/-2.73% of the contralateral hemisphere, respectively. Infarct volume was significantly reduced after treatment with: the intact anti-CD11b antibody upon reperfusion (19.0+/-6.6%) (P<0.05), the fragments of mAbs of anti-CD11b administered upon reperfusion (19.7+/-2.7%) (P<0.05), and at 2 h of reperfusion (22.2+/-4.8%) (P<0.05), and anti-CD18 administered upon reperfusion (20.4+/-4.8%) (P<0.05). Anti-CD11b treatment significantly (P<0.05) inhibited the increase of MPO activity in the ischemic hemisphere. Our data demonstrate that anti-CD11b and anti-CD18 mAb fragments significantly reduce infarct volume and inhibit the increase of MPO activity in the ischemic lesion; administration of anti-CD11b mAb fragment even at 2 h of reperfusion significantly reduces infarct volume. These data support importance of the beta 2 integrin CD11b/CD18 in ischemia/reperfusion injury and indicate that the therapeutic window for intervention to reduce ischemic cell damage in this model is at least 4 h from the onset of MCA occlusion.