There remains to this day a great gap in understanding as to the role of B cells and their products-antibodies and cytokines-in mediating the protective response to Francisella tularensis, a Gram-negative coccobacillus belonging to the group of facultative intracellular bacterial pathogens. We previously have demonstrated that Francisella interacts directly with peritoneal B-1a cells. Here, we demonstrate that, as early as 12 h postinfection, germ-free mice infected with Francisella tularensis produce infection-induced antibody clones reacting with Francisella tularensis proteins having orthologs or analogs in eukaryotic cells. Production of some individual clones was limited in time and was influenced by virulence of the Francisella strain used. The phylogenetically stabilized defense mechanism can utilize these early infection-induced antibodies both to recognize components of the invading pathogens and to eliminate molecular residues of infection-damaged self cells.

Department of Immunology and Gnotobiology Institute of Microbiology of the Academy of Sciences of the Czech Republic Videnska 1083 142 20 Prague 4 Czech Republic

Department of Molecular Pathology and Biology Faculty of Military Health Sciences University of Defence Trebesska 1575 500 01 Hradec Kralove Czech Republic

Department of Toxicology and Military Pharmacy Faculty of Military Health Sciences University of Defence Trebesska 1575 500 01 Hradec Kralove Czech Republic

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