Immunofluorescence detection of human anti-F1 IgG1 mAb (m252) binding to the <i>Y</i>. <i>pestis</i> cell surface.

<p>The mouse anti-<i>B mallei</i> IgG1 (panel A) was used as a nonspecific isotype control. The mouse anti-F1 mAb (F1m) (panel B) was used as a positive control. The binding by the human anti-F1 mAb (m252) is shown in panel C. The rare binding shown with the human anti-V m254 to <i>Y. pestis</i> (panel D) was considered to be the result of autofluoresence because it was seen in both phase contrast and fluorescent microscopy. In the bottom panel E, there was no primary antibody in the reaction before the secondary antibody was added as a negative control.