The agglutination of Proteus vulgaris by cystic fibrosis serum: a re-examination.
The agglutination of the bacterium Proteus vulgaris by serum from cystic fibrosis patients and obligate heterozygotes was shown to be insufficiently specific or reproducible to be of diagnostic value by itself. Approximately 20% of health controls gave a substantial agglutination reaction, whereas the carrier frequency for cystic fibrosis is around 5%. The agglutination did not predominantly involve the bacterial flagella, but appeared to depend on components of the cell surface. The main serum proteins that bind to P. vulgaris cells were shown to be albumin, immunoglobulin G, and complement component C3. In addition, an unidentified protein(s) of low molecular weight was found to bind to the cells. However, no systematic differences were found in the proteins that bind to P. vulgaris cells between cystic fibrosis and normal sera.