Immunological and biochemical relationships among flagella isolated from Legionella pneumophila serogroups 1, 2, and 3.

Flagella were isolated from virulent Legionella pneumophila serogroups 1, 2, and 3. Antiserum made against purified serogroups 1 flagellin agglutinated live, flagellated serogroups 1, 2, and 3 but not heat-killed or nonflagellated bacteria. A single line of identity was seen in immunodiffusion slides between the flagella isolated from the three serogroups and antibody to flagellin isolated from serogroups 1, 2, and 3. Indirect immunoperoxidase staining showed that antibody to flagellin isolated from serogroup 1 organisms reacted with flagella on serogroup 1, 2, and 3 bacteria. Indirect immunoperoxidase staining was also showed that antibody to flagellin isolated from serogroup 1 L. pneumophila did not react with the serogroup-specific cell surface antigen, thus demonstrating that the flagella- and the serogroup-specific antigen are separate antigens. The amino acid content of the flagella from the three serogroups was essentially the same, with aspartate, glutamate, alanine, and threonine comprising 41% of the total. Thirty-five percent of the amino acids were hydrophobic, and there were not detectable amounts of cysteine, tryptophan, or tyrosine.