Crossed immunoelectrophoretic analysis of Legionella pneumophila serogroup 1 antigens.

By crossed immunoelectrophoresis, 85 different antigens were demonstrated in sonicated preparations of Legionella pneumophila serogroup 1 (Lp1). The precipitin patterns of 82 anodic-migrating antigens were numbered and were designated the Lp1 reference system. Eleven antigens were stable to boiling, and seven of these were shown to be surface antigens. One heat-stable surface antigen (antigen no. 61) was highly reactive with limulus amoebocyte lysates and formed a precipitin resembling lipopolysaccharide. Serum from an isolation confirmed case of Lp1 infection and serogroup-specific rabbit antiserum reacted specifically with antigen no. 61, which was designated the serogroup-specific antigen. Normal human and rabbit sera commonly had antibodies to antigen no. 66 of the Lp1 reference system. This antigen is antigenically related to the "common antigen" of Pseudomonas aeruginosa.