Research in cystic fibrosis (third of three parts).

Recent autonomic nervous system studies in cystic fibrosis are outlined. Miscellaneous observations 
regarding salivary and tear glands, calcium, the kallikrein-kinin system, protease inhibitor, 
alpha-fetoprotein, and endocrine glands are discussed. Because more than 90 per 
cent of patients with cystic fibrosis die of progressive pulmonary involvement, 
complicated by infection with Staphylococcus aureus or Pseudomonas aeruginosa (or both), 
the question of immunologic deficit is frequently raised. Extensive investigations have 
shown the immune system in cystic fibrosis to be intact. Studies 
regarding pulmonary ciliary clearance and bacteriology are also outlined. Despite extensive 
investigations, the basic defect of cystic fibrosis is still unknown. What 
then is the explanation of the two defects in homozygotes that 
lead to most clinical manifestations - the sweat electrolyte defect and 
the abnormality in physiochemical behavior of mucous secretions? The former is 
satisfactorily explained by a sodium-reabsorption-inhibitory factor present in sweat and saliva 
of patients. As for the mucous-secretion abnormality, the effect of the 
increasing calcium concentration in decreasing the solubility of glycoproteins suggests that 
this mechanism might be responsible for the precipitation and obstruction of 
organ passages, which gives rise to most symptoms in cystic fibrosis. 
Although there is an excellent diagnostic test for homozygotes (sweat test), 
one cannot rely on any of the present biologic assays for 
determination of heterozygosity or antenatal diagnosis. 