Analysis of the procoagulant and proabortive effects of MBB2. (A) Thrombus formation and (B) vessel occlusion were monitored by intravital microscopy at different time intervals in rats treated or untreated with LPS and infused with MBB2 or control MB. The results are expressed as a ratio between the number of thrombi and the number of microvessels examined and as a percentage of occluded microvessels. (C) Percentage of fetal loss and (D) fetal weight in mice treated with MBB2 or control MB (10 μg/100 µL saline). (E) Sections of rat mesenteric tissue showing vessel occlusion with thrombi in LPS-treated rats receiving MBB2 and small cell aggregates in MBB2-treated animals in the absence of LPS. Both thrombi and cell aggregates were undetectable in the animals treated with control MB. Scale bar equals 50 μm. (F) Representative examples of uteri from a MBB2-treated pregnant mouse showing resorbed fetuses (indicated by arrows) and from a control MB-treated mouse containing live pups. The procoagulant effect of the antibodies was evaluated in 3 rats for each treatment protocol, and the proabortive activity of MBB2 and control MB was tested on ≥5 pregnant mice for each antibody. The data of fetal resorption and vessel occlusion were analyzed with the Mann-Whitney test, whereas the Student t test was used to analyze the data of the fetal weights. The data of vessels occlusion and fetal weight are expressed as mean ± SD; percentages of fetal loss are expressed as median ± interquartile range presented as box plots. *P < .05, **P < .01 vs control MB.