Heterogeneity of antibody response in infection with Legionella pneumophila serogroup 1

The antibody response of patients infected with Legionella pneumophila serogroup 1 in a common source outbreak was investigated. Heat-killed antigens from L pneumophila serogroups 1-3 and 6-10, plus several other strains of L pneumophila, together with 13 other species of legionellas were used in an indirect fluorescence antibody test. Formolised yolk sac antigens made from L pneumophila serogroups 1, 6, and 7 were also used. Although antibodies were produced to several L pneumophila serogroups or Legionella species by individuals, there was no constant pattern, suggesting that the response is a characteristic of the infected individual and not of the infecting strain of Legionella. There is evidence that heat-killed antigen made from L pneumophila serogroup 7 may give unreliable results.