Interactions of Pseudomonas aeruginosa with immunoglobulins and complement in sputum.

The interactions of Pseudomonas aeruginosa with humoral factors in the sputum of 
patients with cystic fibrosis were investigated by using an indirect immunofluorescent 
technique. Fluorescein- conjugated, monovalent antiserum specific to heavy chains of human 
immunoglobulin A (IgA), IgG, or IgM and to complement C3 were 
used. All strains of P. aeruginosa recovered from the sputum specimens 
of patients with cystic fibrosis were found to be coated with 
antibodies of IgA, IgG, and IgM classes and with C3. The 
specificity of the antibody coating was determined. The fluorescence was most 
intense with IgA and was followed in intensity by IgG, IgM, 
and C3. No difference was noted between rough and mucoid strains 
of P. aeruginosa. When the subcultured P. aeruginosa was incubated with 
the sputum eluates, a similar pattern of fluorescence was demonstrated, indicating 
that these humoral factors are present in the sputum and that 
the coating process can take place in the lower respiratory tract 
of the patients. By single radial immunodiffusion, significant quantities of the 
humoral factors in the sputum eluates were detected. These findings suggest 
that P. aeruginosa is opsonized in sputum of patients with cystic 
fibrosis. 