FCGR2B and infection: To further clarify the role of FcγRIIB in the generation of protective immunity against infection, we investigated the impact of FcγRIIB on F. tularensis (Ft) challenge before and after immunization with inactivated Ft (iFt) in WT versus FcγRIIB KO mice. Ft is a gram-negative intracellular pathogen that in designated a Category A biothreat agent due to its extreme virulence [13–15].