Lectins and cystic fibrosis [letter].

Dr Freed and Dr Buckley have shown that a lectin, concanavalin A 
(Con A), causes severe rhinitis, sinusitis, and increased mucus secretion when 
inhaled by man or small-intestinal colic, foul-smelling flatus, and mucus-coated stools 
if ingested. It is somewhat surprising that the authors suggest that 
a suitable inhaled or ingested lectin may be useful in treating 
patients with cystic fibrosis, since the very symptoms produced by the 
ingested lectin resemble those associated with the disease. A more attractive 
recommendation would be for patients with cystic fibrosis to avoid substances 
containing lectins such as Con A to avoid stimulating additional mucus 
release. The underlying pathogenetic defect in cystic fibrosis may be inappropriate, 
excessive stimuli by lectin-like substances. These observations suggest that the increase 
in the protein content of lymphocytes is stimulated by a plasma 
factor present in patients with cystic fibrosis and in carriers of 
the cystic fibrosis gene. These observations, plus those of Freed and 
Buckley, might suggest that cystic fibrosis is a disease involving a 
plasma factor with lectin or Con A-like activity which stimulates the 
secretion of mucus and increases the enzyme content of circulating or 
cultured lymphocytes. - Professor Lieberman confuses cause with effect. If there 
is excessive mucus production in cystic fibrosis we suggest that this 
is because the secretion is so difficult to remove from the 
mucosal surface. Goblet cells and mucus glands become clogged with hyperviscid 
mucus which, not being removed, stimulates further mucus production. To deprive 
the patient of the mucotractive value of his dietary lectins would 
be a therapeutic mischief equivalent to prescribing a cough-suppresant for a 
productive cough. 