The ability of bacteria to activate the terminal complement components in serum of patients with cystic fibrosis.

The terminal complement components, C3 to C9, contribute to the host's defense 
against infection. This study was performed to determine if defective activation 
of C3 to C9 by bacteria contributes to the pathogenesis of 
the recurrent pulmonary infections in cystic fibrosis. When each of the 
bacteria was incubated in the serum of patients with cystic fibrosis 
for 30 minutes, the consumption of available C3 was the same 
as in the sera of the control patients and of the 
two patients with chronic, severe bronchiectasis. Based on the results of 
the present study, it is unlikely that defective activation of C3 
to C9 contributes to the pathogenesis of the increased susceptibility to 
pulmonary infections of these patients. 