Precipitating antibodies against Escherichia coli, Bacteroides fragilis ss. thetaiotaomicron and Pseudomonas aeruginosa in serum from normal persons and cystic fibrosis patients, determined by means of crossed immunoelectrophoresis.

Serum from normal persons and from 133 cystic fibrosis patients was examined 
for precipitins against faecal bacteria (E. coli and B. fragilis) and 
against P. aeruginosa by means of crossed immunoelectrophoresis. 27% of the 
normal sera contained 1-2 precipitins against E. coli, 16% contained one 
precipitin against B. fragilis and 6% contained one precipitin against P. 
aeruginosa. In sera from cystic fibrosis patients, there was a significantly 
increased prevalence of precipitins against E. coli (76%), B. fragilis (38%) 
and P. aeruginosa (63%), and the mean number of precipitins against 
each of these bacteria was 3 (range: 1-12), 1.4 (range: 1-4), 
and 16 (range: 1-60), respectively. Increased numbers of precipitins against P. 
aeruginosa were correlated with chronic lung infection caused by this species 
and with poor prognosis, whereas such associations were not revealed as 
regards precipitins against the two other bacterial species. Increased numbers of 
precipitins against E. coli and B. fragilis were significantly associated with 
increased numbers of precipitins against P. aeruginosa. It is suggested that 
this association is due to immune reactions in the intestinal mucosa, 
resulting in increased absorption of antigens from the gut. 