Studies on ciliary dyskinesia factor in cystic fibrosis. IV. Its possible identification as anaphylatoxin (C3a)-IgG complex.

Presumptive evidence indicates that the substance responsible for the pathophysiologic conditions of 
cystic fibrosis (CF) is a complement component, C3a, also known as 
anaphylatoxin. The known biochemical and physiological properties of C3a, together with 
the behavior of this purified substance when associated with IgG in 
our tracheal bioassay, compare favorably with those of molecular species which 
we have separated from sera and cell cultures of CF homozygotes 
and heterozygotes. Sera from normal healthy subjects, previously inactive by bioassay 
for ciliary dyskinesia factor (CDF), were converted to a CDF positive 
state by incubation with epsilon-amino-caproic-acid (EACA). EACA is a known inhibitor 
of the carboxypeptidase-B-like anaphylatoxin inactivator, and is the method of choice 
for accumulating anaphylatoxins in normal blood. Incubation of EACA-treated normal sera 
and two fresh CDF-positive CF sera with carboxypeptidase-B produced reversion in 
all instances to a CDF negative, normal state. It is proposed 
that anaphylatoxin inactivator, a carboxypeptidase-B-like enzyme, is defective or deficientin cystic 
fibrosis and that this deficiency is the primary gene defect. 