Prolonged neutropenia due to antihuman neutrophil antigen 2 (CD177) antibody after bone marrow transplantation.

We describe a patient who presented with prolonged neutropenia due to anti-human neutrophil antigen (HNA)-2 (CD177) antibody after allogeneic bone marrow transplantation. A granulocyte immunofluorescence test showed bimodal expression of antineutrophil antibody that resulted from specific binding of anti-HNA-2 to CD177+ neutrophils from healthy donors. The patient did not respond to granulocyte colony stimulating factor, which is able to upregulate CD177 expression on neutrophils. The low percentage of CD177+ cells in the few remaining neutrophils supports the possibility of elimination of CD177-upregulated neutrophils. These findings might explain an inferior response to neutrophil growth factors in neutropenia secondary to anti-HNA-2 antibody.