Plasma levels of fibronectin bearing the alternatively spliced EIIIB segment are increased after major trauma

Using Western-blot analysis and enzyme-linked immunosorbent assay (ELISA) of N-deglycosylated samples, we have observed that plasma levels of fibronectin (FN) bearing the alternatively spliced EIIIB segment (EIIIB+ FN) increase in patients after admission to the intensive-care unit (ICU) for acute major trauma. Although not increased at the first sampling (0 hour), taken within 24 hours of ICU admission, levels measured 24, 48, and 72 hours later were significantly increased compared with levels obtained in healthy controls. Furthermore, average concentrations at these latter time points were significantly increased relative to the 0-hour sampling. EIIIB+ FN levels then decreased in plasma samples taken 1 month after hospital discharge, such that no significant difference was found between ELISA-measured values at this time and 0 hour or control values. On the basis of comparisons with previous measurements in these samples, it is apparent that after acute major trauma, circulating levels of soluble EIIIB+ FN exhibit temporal changes that are qualitatively similar to those encountered for FN isoforms bearing the alternatively spliced EIIIA segment (EIIIA(+) FN), yet different from those observed for the total pool of circulating FN. This is the first report of measurement of FN in clinical plasma samples with antibodies specific for the highly conserved EIIIB segment. Like EIIIA(+) forms of FN, EIIIB+ FNs are recognized as soluble bloodborne markers for vascular tissue injury.