When antibodies to P. aeruginosa are used as an index of humoral immunity (chronicity) to P. aeruginosa infection, no relation to avidity of antibodies to BPI was seen in bronchiectasis or bacteremic patients; i.e., high antibody titers to P. aeruginosa are detected equally in patients with low- or high-avidity antibodies to BPI (Fig. 4C). This evidence concerns the gene BPI and bronchiectasis.