Suppression of superantigen-induced lung injury and vasculitis by preadministration of human urinary trypsin inhibitor.

We examined whether the lung injury produced in rats by intraperitoneal injection of the superantigen, staphylococcal enterotoxin B (SEB), could be inhibited by intravenous preadministration of human urinary trypsin inhibitor (UTI), which exhibits multipotent inhibitory effects on serine proteinases such as plasmin, chymotrypsin, or human leukocyte elastase or cathepsin G, since preliminary experiments showed the ability of UTI to bind lipopolysaccharides and bacterial toxins. For ligand blotting analysis, four kinds of toxins were run on a slab gel and the binding of UTI to the toxins was visualized by immunoblotting. Lung tissue from 26 rats was used for immunohistochemistry using a mouse antirat CD 45 mAb and an antirat macrophage mAb. Lung tissue from 31 rats was used for measurement of myeloperoxidase activity before and after intraperitoneal injection of SEB, after infusion of PBS, UTI, PBS-SEB or UTI-SEB combination. Ten of the 26 rats described above were used for electron microscopy. Rat sera were used for measurement of TNF-alpha. Statistical analysis was performed using the Mann-Whitney U-test. Intraperitoneal injection of SEB caused an increase in the number of punctate areas of haemorrhage on the surface of the lung with time, and histological examination revealed lung injuries with different extents, vasculitis where inflammatory cells were concentrated, and infiltration of numbers of eosinophils into the alveolar septa. However, preadministration of UTI for rats markedly attenuated lung injury and vasculitis induced by intraperitoneal injection of SEB. This revealed, from a marked reduction in the number of inflammatory cells and the extent of injury, a marked inhibition of serum TNF-alpha production and reduction of myeloperoxidase content of rat lungs compared to controls. UTI may have defensive effects to infection by suppressing the early responses of stimulated cells to activated stimulus such as SEB as well as the release of stimulant-mediated cytokines via trapping of bacterial toxins.