B hermsii binds to platelets during infection. Blood from uninfected mice or mice infected with 10⁶B hermsii DAH was analyzed at postinfection day 2, that is, at peak spirochetemia. Samples were double-stained with FITC-conjugated anti–B hermsii antibody and PE-conjugated antiplatelet antibody. The percentage of platelets bound to B hermsii was measured by flow cytometry, as described in “Materials and methods.”