Anti‐HNA‐1a antibodies detected in a FcγRIIIb ‘null’ male blood donor

FcγRIIIb ‘null’ individuals do not express the HNA‐1a, ‐1b & ‐1c alloantigens and the reported incidence of this condition in the Caucasian population is between 1 in 1000 and 2000. The majority of FcγRIIIb ‘null’ individuals have been identified following the investigation of neonatal alloimmune neutropenia due to maternally transferred anti‐FcγRIIIb antibodies. This report describes a healthy, male blood donor who was screened for the presence of granulocyte‐specific antibodies as part of a foetal concentration donor accreditation programme. The donor's serum was found to contain anti‐HNA‐1a IgM (and weak IgG) antibodies using an immunofluorescence test. Anti‐lymphocyte antibodies were not detected. Further investigation was undertaken to determine whether the antibodies were alloimmune or autoimmune in origin. Granulocyte membrane bound IgG and IgM was within the normal range and the granulocytes were unreactive both with monoclonal FcRIIIb and HNA‐1a antibodies in immunofluorescence tests. HNA‐1a and HNA‐1b PCR products could not be amplified from the donor's genomic DNA using an SSP technique. It was concluded that the donor was FcγRIIIb ‘null’. The donor denied any history of blood transfusion or surgical procedures; nor was there any evidence of such procedures in early life. This suggests either that HNA‐1a antibodies may, in some circumstances, be ‘naturally occurring’ or that the antibodies detected may be part of an autoimmune response to ‘HNA‐1a like’ structures on other tissues. This is the first time that anti‐HNA‐1a antibodies have been reported in an FcγRIIIb ‘null’ individual. There was no history of transfusion reactions associated with the use of the donor's blood products. However, the donor was withdrawn from the donor panel because HNA‐1a IgM antibodies have been implicated in Transfusion Related Acute Lung Injury.