[1422] Immunophenotypic Study of Basophils by Flow Cytometry

S Ravula, SP Ayar, JM Polski. University of South Alabama, Mobile

Background: Basophils are typically present in low numbers in peripheral blood or bone marrow and usually escape detection by flow cytometry. While the immunophenotypic profile of basophils is known, few studies document the extent of basophil abnormalities. Our aim is to study the normal and aberrant immunophenotype of basophils.
Design: Consecutive cases of peripheral blood and bone marrow specimens (n=12) from patients with increased basophil count and a recognizable basophil cluster on CD45/light scatter gating were studied for immunophenotypic profile of basophils, using 4-color or 8-color flow cytometry. The cases included 5 cases of myeloproliferative neoplasms.
Results: Basophils were recognized by weak to moderate expression of CD45, low forward and side light scatters and a tight cluster adjacent to lymphocytes on CD45/light scatter gating. In most cases, basophils expressed CD11c, CD13, CD22, CD25, CD33, CD36 (heterogeneous), CD38, CD61 (heterogeneous), and CD117 (dim). One case showed expression of CD7, FMC7, and CD56. Basophils were negative for CD19, CD34, and HLA-DR. In some cases, antigen loss or abnormal staining intensity were seen. That included CD11c- (1/12), CD25- (1/12), CD38dim (1/12), CD61- (2/12), CD117- (2/12), and CD22bright (3/12). The number of basophil abnormalities ranged from 0 to 6 per case. The highest number of abnormalities was detected in a case of polycythemia vera. Out of 4 cases of chronic myelogenous leukemia, 2 cases lacked expression of CD117 and one case was negative for CD25.
Conclusions: Our study revealed expression of CD61 (heterogeneous) and CD117 (dim) in basophils. This is surprising as most studies document basophils negative for CD61 and CD117. We also discovered basophil abnormalities that have not been previously reported. While some abnormalities were clustered with myeloproliferative neoplasms, the association was not statistically significant, most likely due to small numbers of cases in this study.
Category: Hematopathology

Tuesday, March 23, 2010 1:00 PM

Poster Session IV # 179, Tuesday Afternoon


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