Pregnancy is associated with a simultaneous but independent increase in circulating CD177pos and immature low-density granulocytes.

Abstract

The neutrophil marker CD177 (NB1, HNA-2a) is expressed by 0-100% of circulating neutrophils in any given donor, dividing neutrophils into two distinct subpopulations (CD177pos and CD177neg). High proportions of CD177pos blood neutrophils have been linked to both systemic infections and a range of inflammatory pathologies, but whether this is a cause or a consequence of disease is not known. Many conditions displaying elevated CD177pos neutrophil proportions are also accompanied by the presence of circulating low-density granulocytes (LDGs). Accordingly, it is tempting to speculate that these two events are connected, i.e., that proportions of CD177pos neutrophils increase as a result of an enlarged pool of circulating LDGs. A temporary increase in CD177pos neutrophils, in combination with the presence of LDGs has been reported during pregnancy. The present study aimed to investigate whether elevated proportions of CD177pos neutrophils in peripheral blood from pregnant women can be attributed to the presence of LDGs. We found that LDGs were indeed present in pregnancy and included both immature, and activated mature neutrophils. The proportion of CD177pos LDGs increased over time during pregnancy and correlated with a simultaneous increase in immature cells. However, a majority of immature neutrophils were CD177neg, meaning that increased release of immature cells cannot explain the increased proportions of the CD177pos subtype. Therefore, although LDGs and CD177pos neutrophils are expanded simultaneously during pregnancy these events occur independent from each other.