On the nature of the defect in cystic fibrosis.

Sera and lymphocyte culture media derived from cystic fibrosis (CF)- affected and 
carrier subjects contain ciliary dyskinesia factor (CDF) detected by our rabbit 
tracheal bioassay. In addition, we also find CDF in fibroblast media 
from these same donors and in amniotic fluid cell media derived 
from CF carrier or affected fetuses. In these latter instances, the 
media were inactive in the bioassay, but became active when mixed 
with purified IgG. In all instances, CDF activity was eliminated by 
the addition of anti-IgG. We have separated a low molecular weight 
fraction, between 1,000 and 10,000 M.W., from CF sera and culture 
media which is inactive in the bioassay until IgG is added. 
Presumptive and indirect evidence indicates that this fraction behaves similarly to 
the complement derived anaphylatoxin C3a. In addition, we have found activity 
in sera from CF patients and, to a lesser extent, carriers 
that induces degranulation of cytochalasin-B- treated human polymorphonuclear leukocytes. Since this 
activity appears to be in a different molecular species from that 
containing CDF, we postulate that the primary defect in CF is 
the deficiency of an enzyme whose substrates include a family of 
membrane-active molecules. 