Definition:

A patient with a mutation in CD16, also known as FcgRIIIa, has been identified. He was a 3-year-old boy, and suffered from recurrent viral respiratory tract infections since birth. CD16 is part of the FcgRIII found on NK cells as well as macrophages and some T cells. The receptor allows NK cells to phagocytose organisms or cells coated with IgG in the absence of MHC (antibody-dependent cellular cytotoxicity). The mutation disrupts NK cell function and is associated with NK cytopenia. The patient also had severe clinical problems after BCG vaccination.