Absence of a serum factor in patients with cystic fibrosis.

A serum factor was demonstrated in normal individuals which (1) enhances the incorporation of L-[3H]fucose into cultured human skin fibroblasts, (2) is nondialyzable, (3) is heat labile at 50 degrees, (4) is present in the noneuglobulin fraction, and (5) appears to be deficient in serum from patients with cystic fibrosis. The specific activity of L-[3H]fucose incorporated into skin fibroblasts from normal individuals in the presence of serum from 12 control subjects was 3,337 +/- 168 cpm/mg protein in contrast to 2,294 +/- 172, the activity obtained either in the presence of serum from 10 age-matched patients with cystic fibrosis or in the absence of serum. These differences were significant at P less than 0.001. In comparison, no significant difference was detected in the amount of L-[3H]fucose incorporated into skin fibroblasts derived from normal individuals and patients with cystic fibrosis. The plasma membrane of cultured skin fibroblasts derived from patients with cystic fibrosis appears to be grossly unaltered in its protein and L-fucose labeling pattern.