Exclusive neutrophil recruitment with oncostatin M in a human system.

Oncostatin M (OSM), a member of the IL-6 family has been postulated to be a potent recruiter of leukocytes, however information regarding the molecular mechanism(s) underlying this event is extremely limited. Therefore, the aim of this study was to investigate the role of OSM-mediated leukocyte recruitment in a human system in vitro under flow conditions. A parallel-plate flow chamber assay was used to examine leukocyte recruitment from whole blood by human umbilical vein endothelium treated for 24 hours with OSM. OSM in a dose-response manner revealed very significant leukocyte rolling and adhesion reaching optimal levels at a very low concentration of OSM (10 ng/ml). The OSM-induced leukocyte rolling and adhesion was comparable to levels seen with tumor necrosis factor. OSM was extremely selective for neutrophil recruitment (96%) with <3% lymphocyte recruitment. By contrast, tumor necrosis factor-alpha revealed no such selectivity, recruiting 70% neutrophils and at least 25% lymphocytes and detectable levels of eosinophils at 24 hours. The molecular mechanism underlying the leukocyte recruitment seemed to be entirely dependent on P-selectin as leukocyte recruitment could be completely blocked by the addition of a P-selectin-blocking antibody. An elevation in both P-selectin message and protein was observed with 24 hours of OSM stimulation of endothelium. By contrast, E-selectin and VCAM-1 were not detectable after OSM stimulation. Similar results were seen with passaged dermal microvascular endothelium that does not have a prestored pool of P-selectin. Based on these results, we conclude that OSM may be a very selective potent recruiter of neutrophils in more prolonged inflammatory conditions, an event exclusively dependent on P-selectin.

Leukocyte recruitment in the microcirculation: the rolling paradigm revisited.

Intravital microscopy has done much to elucidate the cascade of events involved in the recruitment of leukocytes to sites of inflammation. Here we review the physiological relevance of leukocyte rolling and some of the important subtleties of this process, highlighting limitations in our knowledge and directions for future investigation.

Autoantibodies from patients with idiopathic ataxia bind to M-phase phosphoprotein-1 (MPP1).

In an attempt to identify unique disease-related autoantibodies, the serum from an ataxia and sensory neuropathy patient was used as a probe to isolate a 2.5-kd cDNA from a HeLa expression library. The nucleotide sequence was 99% identical to MPP1, a cell-cycle-related nuclear protein phosphorylated during mitosis. Expression of the cDNA in an in vitro translation system yielded a recombinant protein that migrated in SDS-PAGE at approximately 97 kd. This protein was immunoprecipitated by the prototype human serum, by an immune guinea pig anti-MPP1 serum, but not by normal human serum or preimmune guinea pig serum. Western blot analysis of HeLa cell proteins showed that the prototype human serum and immune guinea pig antiserum recognized an approximately 225-kd protein, suggesting that the isolated clone contained a partial cDNA. By indirect immunofluorescence, the affinity-purified antibody and a guinea pig antiserum reacted with nuclei of interphase HEp-2 cells and the cytoplasm of certain neuronal cells. Sera from 10 of 25 unselected patients with ataxia, 1 of 30 patients with peripheral neuropathy, 1 of 50 multiple sclerosis patients, 0 of 20 amyotrophic lateral sclerosis, 0 of 10 children with postviral ataxia, 0 of 10 systemic lupus erythematosus patients, 0 of 3 patients with hereditary cerebellar ataxia, 0 of 8 with ataxia telangiectasia, and 0 of 30 age- and gender-matched controls immunoprecipitated the recombinant MPP1 protein. None of the patients with anti-MPP1 antibodies had evidence of malignancy. This is the first report of MPP1 as a target autoantigen in patients with idiopathic ataxia.