Amount and Avidity of IgG Antibodies to Pseudomonas Aeruginosa Exotoxin A Antigen in Cystic Fibrosis Patients.

Amount and avidity of serum IgG antibodies to Pseudomonas aeruginosa exotoxin A in sera of 31 patients with cystic fibrosis (CF) was studied. Eight patients had P. aeruginosa isolated from the sputum on multiple occasions, while from 23 patients no P. aeruginosa was isolated. Amount of IgG antibodies to P. aeruginosa exotoxin A were significantly increased in the serum of patients with P. aeruginosa pulmonary colonization (p<0.0001). On the contrary, serum IgG avidity in the colonized and in the non-colonized CF patients was low (<10) and was statistically different when compared to the 30 age-matched healthy controls (p<0.0001). There was no change in IgG avidity in six chronically infected CF patients from whom we obtained serum samples after half a year period (p=0,55).