Little impact of donor/recipient major mismatch for neutrophil-specific antigen NA2 on neutrophil recovery after allogeneic SCT.

The Fcγ receptor IIIb (FcγRIIIb), a receptor for the Fcγ region of IgG, is specifically expressed on neutrophils. It has two allelic polymorphisms, NA1 and NA2, which are highly immunogenic and act as targets in alloimmune or autoimmune neutropenia. Thus, neutrophil antigens (NA) compatibility of donor/recipient pairs might be expected to affect the engraftment of neutrophils after allogeneic SCT (allo-SCT). Here, the impact of NA compatibility of 17 patients and their donors undergoing allo-SCT with a myeloablative regimen was determined. Leukocyte depletion filters were used for all transfusions before and post-SCT; most patients received G-CSF after transplant. Major mismatches for NA1 and NA2 were present in 1 and 7 patient/donor pairs, respectively. These eight patients receiving NA major-mismatched allo-SCT were compared with nine patients who received NA compatible allo-SCT. Engraftment of neutrophils and the incidence of post-engraftment neutropenia were found to be identical in the two groups. Despite the limitations in statistical power because of the small number of patients analyzed, these observations suggest that the major mismatching for NA2 antigen has little impact on the engraftment of neutrophils after myeloablative allo-SCT, at least in patients transfused using leukocyte depletion filters and receiving G-CSF after transplantation.