Abstract
Localization and characterization of human platelet-derived adhernce-inhibiting factors (AIFs) were studied. Subcellular fractionation experiments showed that AIFs were present in both cytosol and granule fractions of human platelets. When cytosol and granule fractions of human platelets were applied to a Superose 6 column, the adherence inhibiting activity of the cytosol fraction was eluted at two different positions (2, 600 and 480 kDa), whereas that of the granule fraction was eluted as a single peak (2, 600 kDa) . Thrombinstimulated platelets released granular AIF extracellularly without releasing a cytosolic marker.
When the purified AIF was analyzed on SDSPAGE, the 340 kDa protein band and the other large protein bands were observed. Under reducing conditions, AIF was separated into two components (340 and 190 kDa) . The purified AIF inhibited human neutrophil adherence to glass, plastic and type IV collagen-coated plastic, whereas it did not affect neutrophil adherence to fibronectin- or plasma-coated plastic. AIF inhibited neutrophil spreading on glass. Neither monocyte adherence nor monocyte spreading was affected by AIF.
These results indicate that AIF selectively affects neutrophil adherence and spreading among phagocytic cells.
