Abstract • 199

Recent recognition of the genetically-determined abnormal chloride channel in CF patients which promotes viscous secretions and impaired mucociliary clearance together with the massive accumulation and disintegration of neutrophils with release of proteolytic enzymes are believed to be responsible for inflammation, bacterial colonization, immunoglobulin cleavage, and production of cytokines which ultimately determine the fate of either protective immunity or colonization with PsA. Previous studies from our laboratory have examined the nature of immunoglobulin content in sera and gastrointestinal secretions (Kulczycki et al, Clin. Proc. Child. Hosp. 34:290, 1978). More recently we have studied the spectrum of anti-pseudomonas antibodies in nasal secretions and sera in 10 PsA-colonized (PsA+) and 6 PsA-non-colonized (PsA-) CF patients compared to 10 control subjects. The results of the study, thus far, have revealed the following: 1) Fisher immunotype 9 was the most frequently isolated; 2) Significant elevations of serum IgA and nasal IgA antibody to PsA were detected to a greater degree in CF (PsA+) patients than in either CF (PsA-) or in controls. The results of the present studies lend further support for the biologic role of IgA in protective immunity-colonization with PsA and provide a basis for the development of live attenuated PsA vaccines which can induce mucosal immunity in patients with CF.