Human basophils express CD22 without expression of CD19

Background: Even modem automatic cell counters cannot count basophils preci sely. Therefore, Re need a rapid, accurate, precise, and easy method for co unting basophils. Methods: Using flow cytometry, basophils (CD22+/CD19-) and B cells (CD22+/C D19+) were counted. Within a large lymphocyte light scatter gate, % basophi ls (G%baso) and % B cells (G%B) were determined from the total count. Anoth er method of analysis was to make two regions (R1 for basophils and R2 for B cells) and to determine in these the % basophils (R1%baso) and % B cells (R2%B) without gating. The flow cytometric basophil counts of the blood of 21 normal controls and 43 chronic myelogenous leukemia (CR IL) patients wer e compared with manual basophil count (Ma%baso) and basophil count by Coult er electronic cell counter (Hialeah. FL) (Auto%baso). CD22+/CD19- cells wer e sorted by a FACSCalibur (Becton Dickinson, SanJose, CA). Results: The G%baso of all samples was 4.66 +/- 5.35%, and R1%baso was 4.23 +/- 4.88%, and they were well-correlated (r = 0.996, P < 0.001). The G%B o f all samples was 1.55 +/- 1.68%, and R2%B was 1.59 +/- 1.67%, and they wer e also well-correlated (r = 0.933, P < 0.001). Their correlation was better in normal controls than in CML. G%baso was well-correlated to Ma%baso (r = 0.827) and Auto%baso (r = 0.806), and R1%baso was well-correlated to Ma%ba so (r = 0.831) but showed poor correlation to Auto%baso (r = 0.734) Auto%ba so revealed the poorest correlation to Ma%baso (r = 0.692). The sorted CD22 +/CD19- cells were all basophils (99.48 +/- 0.30%), and they revealed CD13, CD33, and dim CD45 expression, whereas CD3, CD14, CD16, and HLA-DR mere no t detected on them. Conclusions: We discovered a specific marker combination to identify basoph ils (CD22+/CD19-), and we suggest that flow cytometric analysis using these markers is an easy, reliable, and accurate method of basophil counting. Cy tometry 37:178-183, 1999. (C) 1999 Wiley Liss, Inc.