IgG and IgA autoreactivity to BPI in CF patients was demonstrated in serum and BAL, respectively, and correlated with the isotype of the antibody response to P. aeruginosa.
In the CF group, platelet aggregation correlates with levels of anti-neutrophil cytoplasmic antibodies (ANCA) with specificity for bactericidal/permeability-increasing protein (BPI), BPI-ANCA (r=0.56).
The presence of BPI-ANCA was associated with the number of antibiotic courses, low body mass index, Pseudomonas aeruginosa colonisation, the presence of resistant P. aeruginosa, low forced expiratory volume in 1 s, CF-related liver disease, hypergammaglobulinaemia, male sex and inflammatory syndrome.
Thus, BPI that is functionally active against mucoid P. aeruginosa strains is expressed in the airways of CF patients but may be hampered by autoantibodies, resulting in chronic infection.
BPI represents a major ANCA target antigen in patients with rheumatological as well as inflammatory bowel disease and cystic fibrosis, but AZ-ANCA are uncommon.
Circulating ANCA specific for bactericidal/permeability increasing protein (BPI) have been recently reported in adult patients with cystic fibrosis (CF), an autosomal recessive disorder caused by mutations in the cystic fibrosis transmembrane regulator (CFTR) gene with consequent impaired function of a transmembrane chloride channel.