Single-site, five-year experience with human eosinophil isolation by density gradient centrifugation and CD16 immunomagnetic negative separation

Objective: Little has been reported regarding the reliability of methods for the purification of human blood eosinophils. We retrospectively reviewed our experience with 350 consecutive eosinophil isolations. Results: Between January 2014 and December 2018, we conducted 350 eosinophil purifications from 83 donors. Absolute eosinophil count (AEC), calculated from hospital complete blood counts when available (n = 289), ranged from 32 to 1352 eosinophils/μL ($$\bar{x}\pm {\text{SD}}$$ x ¯ ± SD: 179 ± 136/μL). Eosinophil yields ranged from 0.4 to 24.4 million cells per 20 mL of blood drawn ($$\bar{x}\pm {\text{SD}}$$ x ¯ ± SD: 3.1 ± 1.9 million eosinophils) with > 98% purity. Comparing AEC to actual yield, recovery was 87% ± 29% ($$\bar{x}\pm {\text{SD}}$$ x ¯ ± SD) and AEC strongly correlated with yield. To explore the reproducibility of yield, a subsequent analysis was limited to those donors drawn ≥ 3 times (N = 35), and there was no difference in the average coefficient of variation for yield between allergic and non-allergic donors. Viability of isolated eosinophils was consistently > 95% and after 24 h of culture did not differ between allergic and non-allergic donors. We conclude that this immunomagnetic separation method for human eosinophil isolation from whole blood is a reliable, reproducible technique for obtaining an average of 87% yield with high purity and viability.