FCGR2A and neoplasm: To ascertain the role of FcγRs in MGAH22 anti-tumor activity, xenograft studies employed three mouse strains: FcγR-WT mice (WT murine FcγR repertoire), mCD16-/- mice (lacking murine CD16), and mCD16-/- hCD16A+ mice (lacking mCD16 but transgenic for human CD16A-158F, the low-binding allele).