Distribution of complement C3 variants in individuals with cystic fibrosis.

The gene frequency for slow and fast electrophoretic variants of complement C3 
in Caucasian individuals with cystic fibrosis was similar to the values 
expected for unaffected controls, thereby ruling out a suspected differential involvement 
of these phenotypes with the disease. In one family, cystic fibrosis 
and complement C3 phenotypes segregated independently. 