Reactivity of serum from patients with suspected legionellosis against 29 antigens of legionellaceae and Legionella-like organisms by indirect immunofluorescence assay

J Infect Dis. 1983 Jan;147(1):23-31. doi: 10.1093/infdis/147.1.23.


Sets of sera (444) submitted for diagnostic testing for legionellosis were tested against 29 indirect immunofluorescence assay (IFA) antigens prepared from the characterized Legionella species and Legionella-like organisms to determine the prevalence of antibodies to Legionella organisms. Reciprocal titers of 15% of the serum sets rose fourfold or more to greater than or equal to 128 (indicating seroconversion) against one or more Legionella antigens. The specificity of the test was 96% when evaluated in patients with pneumonia due to non-Legionella organisms. Antibodies were of the IgG, IgM, and (infrequently) IgA classes and were either specific for a single species (as defined by a difference in titer of fourfold or more) or reacted with common Legionella antigens (30 [45%] vs. 36 [55%] of 66 seroconversions, respectively). No single antigen detected half of the positive sera. Elevated IFA titers (of greater than or equal to 256) against single or multiple Legionella antigens occurred in 12% of 184 normal control sera. Therefore, only seroconversions to titers of greater than or equal to 128 should be considered indicative of recent Legionella infection.

MeSH terms

  • Antigens, Bacterial / immunology*
  • Epitopes / analysis
  • Fluorescent Antibody Technique
  • Humans
  • Immunoglobulin A / analysis
  • Immunoglobulin G / analysis
  • Immunoglobulin M / analysis
  • Legionella / immunology*
  • Legionnaires' Disease / diagnosis*
  • Legionnaires' Disease / immunology
  • Pneumonia / immunology
  • Pneumonia / microbiology


  • Antigens, Bacterial
  • Epitopes
  • Immunoglobulin A
  • Immunoglobulin G
  • Immunoglobulin M