Activated low-density granulocytes in peripheral and intervillous blood and neutrophil inflammation in placentas from SLE pregnancies

Abstract

ObjectiveWomen with SLE face an increased risk of adverse pregnancy outcomes compared with healthy women, but the underlying immunological mechanisms are unknown. Given the recognised association of neutrophil activation with SLE pathogenesis, we examined whether there is increased neutrophil activation and inflammation in blood and placenta in SLE relative to healthy pregnancy.MethodsAt delivery, peripheral blood, maternal-derived intervillous blood and placentas were collected from 12 SLE and 10 healthy control pregnancies. The proportion of low-density granulocytes (LDGs) and the activation status of LDG and normal-density granulocytes were examined with flow cytometry. The chemokines CXCL8 and CXCL1 were quantified with a cytometric bead-based assay and interferon alpha (IFNα) protein levels with a Simoa method. IFNα-stimulated maternal-derived decidual stromal cells were examined for CXCL8 gene expression with qPCR. A pathologist, blinded to the patient background, examined all placentas.ResultsWomen with SLE had significantly higher proportions of LDG in peripheral blood compared with controls (p=0.02), and LDG in both peripheral and intervillous blood were more activated in SLE relative to healthy pregnancies (peripheral blood: p=0.002 and intervillous blood: p=0.05). There were higher levels of CXCL8 and CXCL1 in intervillous compared with peripheral blood in women with SLE (p=0.004 and p=<0.0001, respectively) but not in controls. In SLE pregnancy, IFNα was detectable in 6 out of 10 intervillous blood samples but only in one control. Stimulation with IFNα upregulated CXCL8 gene expression in decidual stromal cells from both SLE and healthy pregnancy. Histological chorioamnionitis was present in 6 out of 12 placentas from women with SLE and in 1 out of 10 controls.ConclusionsIn women with SLE, locally produced chemokines in the placenta are increased and may attract and activate neutrophils. This in turn could contribute to placental inflammation and dysfunction and increased risk of placenta-related pregnancy complications.

Myeloperoxidase and Other Markers of Neutrophil Activation Associate With Malaria and Malaria/HIV Coinfection in the Human Placenta

“…Importantly, CXCL8 is elevated in PM+HIV+ placentae. The source of CXCL8 in the placenta that might participate in this response is not clear but could be maternal monocytes ( 22 , 26 ), fetal syncytiotrophoblast ( 3 , 22 , 81 , 82 ), or uterine/decidual stromal cells ( 83 ).…”

Neutrophils in pregnancy: New insights into innate and adaptive immune regulation

“…Granulocyte MDSCs and another subpopulation of neutrophils called low‐density neutrophils (LDNs) share similarities in that they are both found in the low‐density fraction following density gradient centrifugation and share several surface markers including CD66b, CD15 and CD33 [ 48 ]. LDNs were first described in patients with systemic lupus erythematosus where they exhibited pro‐inflammatory functions [ 49 ]. LDNs are increased both in pregnant SLE patients and in healthy pregnant patients but have contrasting functions.…”

“…LDNs are increased both in pregnant SLE patients and in healthy pregnant patients but have contrasting functions. LDNs from pregnant SLE patients are inflammatory, whereas LDNs from healthy pregnancies express high levels of arginase and therefore are presumed suppressive [ 49 , 50 ]. The contrasting functions of seemingly phenotypically similar neutrophils have led to the description numerous neutrophil subsets within the literature.…”

Radiographic airway abnormalities in untreated early rheumatoid arthritis are associated with peripheral neutrophil activation

“…The increased activation of neutrophils in patients with PA was found in normal density granulocytes but not in LDGs. The proportion of LDGs in this ueRA cohort was low compared to systemic lupus erythematosus [ 15 ]. Whether there is an association of frequency and/or activation of LDGs and lung disease in RA needs to be evaluated in further studies.…”

“…within 1 week from diagnosis and before initiation of treatment). All analyses were performed within 6 h. Neutrophils were separated using density centrifugation (Ficoll-Paque Plus, Cytiva, Sweden), in this paper referred to as low-density granulocytes (LDG) and normal density granulocytes (NDG), and subjected to flow cytometry as previously described [ 15 ]. Activation of neutrophils was assessed by expression of CD11b and CD62L.…”