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. 