Immunophenotypic Study of Eosinophils by Flow Cytometry
Jacek M Polski. University of South Alabama, Mobile, AL
Background: Eosinophils are typically present in low numbers in peripheral blood or bone marrow and usually escape detection by flow cytometry. While the basic immunophenotypic profile of eosinophils is known, few studies documented eosinophil abnormalities in reactive or neoplastic conditions.
Design: Cases of peripheral blood or bone marrow specimens (n=24) from patients with increased eosiniphil count and/or a recognizable eosinophil cluster on CD45/light scatter gating were studied for immunophenotypic profile of eosinophils, using 4-color or 8-color flow cytometry. The cases included 14 myeloid neoplasms (8 cases of acute myeloid leukemia and 6 cases of chronic myelogenous leukemia).
Results: Eosinophils were recognized by moderate expression of CD45, moderate forward and very high side light scatters. They formed a poorly defined cluster above mature neutrophils on CD45/light scatter gating. Eosinophils had high levels of autofluorescence. In most cases, eosinophils stained for CD11c, CD13, CD15, CD33, CD38, CD65, and CD61 (partial). While this immunophenotype was similar to one in neutrophils, no expression of CD10 or CD16 was seen in eosinophils. Rare cases showed staining for HLA-DR, CD4, CD23, CD25, CD36, or CD71. CD4 was more common in reactive conditions (4/10) versus myeloid neoplasms (0/14). The difference was statistically significant (Yates' Chi-Square test p=0.04) despite low number of positive cases.
Conclusions: This study documents the expression of several myeloid markers in eosinophils. This adds to the published literature on eosinophils. The results suggest that subtle immunophenotype differences may exist between neoplastic and reactive eosinophils.
Wednesday, March 21, 2012 1:00 PM
Poster Session VI # 249, Wednesday Afternoon