Inhibition of the adherence of Pseudomonas aeruginosa to epithelial cells by IgG subclass antibodies.

A beneficial role of the antibody response to Pseudomonas aeruginosa seen in cystic fibrosis (CF) patients has not been established. We investigated a possible role for these antibodies as inhibitors of the adherence of P. aeruginosa to mammalian cells. An adhesion model system was used, employing buccal epithelial cells in an enzyme-labelled immunoassay procedure on microtitration plates. Total levels of IgG, IgA, IgM and the four IgG subclasses were estimated in 11 CF patients and 10 healthy controls. Most of the CF patients demonstrated increased levels of all these immunoglobulin types. Sera from seven patients with elevated serum IgG were observed to cause greater inhibition of the adherence of P. aeruginosa to buccal cells than were the sera from four CF patients with low serum IgG and from ten healthy controls. Nevertheless, the levels of individual anti-P. aeruginosa IgG subclass antibodies varied amongst the patients and did not correlate with the degree of inhibition of bacterial adherence. Negative affinity chromatography was used to obtain antibody fractions enriched for IgG1, IgG2 or IgG4 and protein A-sepharose chromatography was used to isolate IgG3 antibodies from CF patients. The IgG1-, IgG2-, or IgG4-enriched fractions similarly inhibited the adherence of P. aeruginosa in the test system, whereas three of five IgG3-enriched fractions from CF patients had no greater effect on adhesion than did IgG from control individuals.