Letter: Complement in cystic fibrosis.

Lieberman reported that there was considerable overlap in quantitative C3 levels between 
all of the C.F. subjects tested, and the control group. His 
control group, however, was composed of subjects with bronchiectasis or chronic 
bronchitis, in whom C.F. had been ruled out. The use of 
a more proper control group by Lieberman, either in place of 
or in parallel with his "diseased" control groups, would have provided 
a more meaningful interpretation concerning the role of complement in cystic 
fibrosis. We agree that there is a tendency for C3 to 
be higher in C.F. females than in C.F. males. Although Lieberman 
was quick to dispel any notion of C3a being implicated in 
the aetiology of C.F., he overlooked the one facet of our 
initial study that still makes our hypothesis feasible - raised C3 
levels in C.F. obligate heterozygotes. Hann et al. reported that serum-C5 
was raised in both C.F. patients and their parents. Our initial 
data on C5 levels by radial immunodiffusion and haemolytic studies do 
not confirm this finding. We are supporting the hypothesis that C.F. 
is either a complement-caused or complement-mediated disorder, in which a C3a-like 
molecule (C3a, bradykinin) either alone or by complexing with IgG gives 
rise to the physiological and pathological state of C.F. 