['The Duffy blood group (Fy) antigen functions as the receptor whereby the malarial parasite Plasmodium vivax invades reticulocytes. In this study, we evaluated an autologous blood donation model to measure Fy expression during the anticipated response to blood loss.', 'This study aims to examine Fy expression following anticipated reticulocytosis in response to blood loss from autologous whole blood donation.', 'Subjects were healthy blood donors presenting for planned collection of two or three autologous units. Whole blood (450 ml +/- 10%) was collected and processed. Blood samples for Fy testing were obtained from the donations. These were assayed by flow cytometry by measuring binding of a phycoerythrin-labelled anti-Fy6 antibody and compared against reticulocyte numbers. Reticulocyte numbers were measured using thiazole orange. Results were compared from baseline (first donation) with samples at second and, if available, third, donations. Phenotyping for Fy a and b antigens was performed.', 'Reticulocytes increased by a mean of 37% over baseline [0.93% (range 0.31-1.93) to 1.23% (0.32-3.51%)] following donation of two (n = 32) or three (n = 9) autologous whole blood units. Absolute reticulocyte count remained low. Mean and median Fy expression on mature red blood cells and reticulocytes did not change from baseline levels despite individual variation. No apparent relationship to serologically determined Fy a and/or b antigen status was present.'] Does duffy antigen expression on reticulocytes alter following blood loss in an autologous donation model?