Cystic fibrosis: studies with the oyster ciliary assay.

Bioassays using ciliary systems have detected a factor or factors in cystic 
fibrosis (CF) sera and tissue culture medium derived from CF cells. 
The typical shortcomings of an assay measuring biological activity have been 
studied, and the means to overcome the weaknesses of the oyster 
gill cilia assay have been established. The presence of the cystic 
fibrosis mucociliary inhibitor (CFMI) in experimental fractions may be determined by 
accepting data from only those assays in which authentic CF and 
normal (non-CF) fractions give defined reactions, by measuring the reaction of 
each sample at least three times, and by examining each experimental 
sample at a protein concentration greater than the minimum established in 
this study. The relative concentrations of the CFMI present in the 
first steps of purification of serum and medium have been calculated 
in terms of units of inhibition. Generally, the units of inhibition 
present in serum and medium fractions from heterozygotes are close to 
one-half of that in fractions from homozygous sources. Analogous fractions concentrated 
from a normal (non-CF) source never inhibited mucociliary activity, even when 
tested at nearly 100 times the CF concentration. Ciliary assays utilizing 
oyster gills are essential for monitoring fractionation procedures aimed at purifying 
the CFMI, and have been shown to be capable and reliable 
enough to do so. 