Antibodies against Legionellaceae in the population of West Germany and their methodical determination

The preparation of antigen (L. pneumophila serogroups 1--4 and L. micdadei) was performed by heat killing at 70 degrees C for 5 min as the most conservative method. The serological investigations used the indirect immunofluorescence assay (IF) and the microagglutination test (MA). No clear differences were observed between sera of normal and suspicious human beings and between sera of males and females. Young people has the highest percentage of low titers. L. pneumophila serogroup 1 produced the highest titers. Comparison of IF and MA showed that the cutoff level of MA is two to three steps lower than that of IF. About one percent of the sera investigated showed significant antibodies. They decrease with an half life time of 3--4 weeks.