Aims: Blood contact with foreign surfaces in the apheresis systems may activate many cell types that return back to the donor. However, the safety issue regarding post-procedure platelet activation is not well assessed. We aimed to evaluate the alterations in hematological parameters and to explore the formation of platelets leukocytes aggregates (PLAs) and/or complexes in healthy donors who underwent first-time plateletpheresis procedure.

Methods: Blood from 100 healthy donors were assessed by BD FACS Calibur flow cytometer for: a) detection of PLAs using (CD41, CD42b, CD61) antibodies against platelets surface molecules to detect its expression on neutrophils, monocytes, lymphocytes, and b) evaluation of red cell mechanical fragility (RBC-MF).

Results: After donation a significant decrement of donor blood cell counts; the percent (%) reduction in hemoglobin (Hb) 7.9(5.1–9.2) (p = 0.017), hematocrit (Hct) 6(2.72-7.81) (p = 0.043) %, residual red cells (p = 0.016), platelet count (PLT) 22.7(9.5–32) (p = 0.031) together with a significant increase in the MPV (p = 0.001), the absolute neutrophil (p = 0.026) and lymphocyte count (p = 0.041) with an insignificant increase in absolute monocyte (p = 0.103), lymphocyte subsets count, CD4:CD8 ratio, and WBC count. However, there was significant increase in the median platelets complexed with neutrophil, lymphocytes, and monocytes.

Conclusion: All donors had a significant drop in all blood counts; none of them manifested features of thrombocytopenia or anemia. However, an increase in PLAs formation provides an evidence of ongoing platelet activation, a platelet-leucocyte interaction that may induce a pre-thrombotic risk. This result is important to consider as it might have potential therapeutic implications. Nevertheless, more prospective studies are essential to establish guidelines for donor safety.

Keywords: Donor safety, Flow cytometry, Platelet-leukocyte aggregates, Single donor platelet