The greatest diagnostic significance for tularemia is played by antibodies against lipopolysaccharide (LPS). Previously, it has been shown that specific antibodies that appear in the blood serum of laboratory animals infected with virulent strains and people who have recovered from tularemia can bind both to LPS Francisella tularensis and to LPS Francisella novicida, while after the vaccination specific antibodies to LPS F. novicida are absent.