Heterogeneity of peripheral blood reticulocytes: A flow cytometric analysis with monoclonal antibody HAE9 and thiazole orange

The expression of a human erythroid cell surface antigen recognized by monoclonal antibody (mAB) HAE9 has been studied on peripheral blood reticulocytes by one‐ and two‐color flow cytometry. Total reticulocyte count was determined using Thiazole Orange (TO) and flow cytometry. In normal individuals, 4.56% of reticulocytes were stained by FITC‐labeled mAB HAE9. The correlation between reticulocyte percentage by TO and HAE9 staining was 0.828 (P < 0.0001) in patients with hematocrits less than 0.25. A HAE9‐positive reticulocyte percentage of 6–44% was observed when analyzed by two‐color flow cytometry with TO and mAB HAE9. These findings, in conjunction with previous studies, suggest that mAB HAE9 recognizes an early, less differentiated population of peripheral blood reticulocytes. Enumeration of immature reticulocytes may be of clinical utility.