Iso-immune neonatal neutropenia due to an anti-Fc receptor III (CD16) antibody.

We report a case of transient neonatal neutropenia due to a maternal iso-immunization against a non polymorphic region of the glycosylphosphatidylinositol-linked Fc receptor type III (CD16) on granulocytes. The mother's granulocytes were typed NA1-negative, NA2-negative and CD16-negative with human and monoclonal antibodies whereas her lymphocytes express the CD16 molecule. Expression of other markers were comparable to the controls. Flow cytometric analysis showed that maternal antibody recognized the granulocytes but not the lymphocytes from blood bank donors and that its binding was decreased on normal, phospholipase C-treated, granulocytes. The binding of commercial CD16 monoclonal antibodies was also dramatically decreased on normal granulocytes pre-incubated with maternal serum. The CD16 specificity of the antibody was confirmed by negative reactions with another CD16-deficient granulocytes. This observation leads us to conclude that cell-lineage specific differences of CD16 molecules are recognized by the patient's antibody. Moreover, we confirm that the absence of the FcRIII (CD16) on granulocytes is not associated with any pathology or susceptibility to infections and that, in the children, the blockade of this receptor by the maternal antibody only led to moderate neutropenia.