Recently an interesting investigation was published in Vox Sanguinis concerning in vitro evaluation of buffy coat derived granulocytes for the therapeutic use. Normally patients, who need granulocytes, are critically ill. Facing the fact, that conventional produced granulocyte concentrates contain 30 to 50 mL hydroxyethyl starch which is actually not approved for critically ill patients, this publication offers a promising possibility to produce sufficient granulocytes without the exposure to hydroxyethyl starch for both, patients and donors.

Routinely granulocytes (GTX) for the therapeutic use are collected by apheresis technology from rh-GCSF and/or steroid pretreated volunteers. Hydroxyethyl starch (HES) as sedimentation agent is crucial for an efficient collection. Since the negative impact of HES on the outcome in critically ill and septic patients is known several, medical societies like FDA, EMA … have withdrawn their regulatory approval for HES in these medical settings.
 In brief:
The authors collected buffy coat derived granulocytes (BCN) (a byproduct of whole blood collection), pooled in sum ten buffy coats and created a so called “super” buffy coat of small volume and high purity (> 95% granulocytes, low red cells and low numbers of platelets). They performed a lot of viability test, function test and assessed surface markers like maturation markers (EMR3), adhesion molecules (L-selectin = CD62L), integrin C3 and Fcy receptors on these granulocytes. Additionally microbial killing was assessed. Survival test of BCN were performed with (to mimic in vivo conditions) and without rh-GCSF incubation All data were compared to conventional collected granulocytes and to granulocytes of untreated controls.
In summary, BCN were not inferior in basic functions, showed no increased activation markers due to manipulation, had a normal maturation status (which is not found in conventional GTX, probably due to mobilization induced immature release from the bone marrow) and a satisfactorily survival after GCSF incubation. Also the killing mechanism was comparable to GTX and controls and even more efficient in Candida albicans eradication comprared to GTX. GTX granulocytes are known to have a significantly reduced killing capacity for C.albicans, probably due to their immature status.
A drawback may be the rather low numbers of granulocytes in BCN, but this can easily be compensated by transfusion of two or more of these pure small volume BCN units.

A. van de Geer, R. P. Gazendam, A. T. J. Tool, J. L. van Hamme, D. de Korte, T. K. van den Berg,  S. S. Zeerleder & T. W. Kuijpers
Vox Sanguinis (2017)© 2017 International Society of Blood TransfusionDOI: 10.1111/vox.12481
Summary (by Gerda Leitner)