ePoster Presentation 49th Annual Scientific Meeting of the Australian and New Zealand Society for Immunology 2021

Extracellular traps are prevalent in bronchoalveolar lavage from children with non-cystic fibrosis bronchiectasis (#158)

Amy S Bleakley 1 , Steven Kho 1 , Michael J Binks 1 , Susan Pizzutto 2 , Anne Chang 1 3 , Gabriela Minigo 1 4 , Robyn Marsh 1
  1. Menzies School of Health Research, Charles Darwin University, Darwin, NT, Australia
  2. Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, NT, Australia
  3. Queensland Children's Hospital, Centre for Children's Health Research , Brisbane, QLD, Australia
  4. College of Health and Human Sciences, Charles Darwin University, Darwin, NT, Australia

Background: The mechanisms underlying pulmonary inflammation in children with non-cystic fibrosis bronchiectasis (BE) are poorly understood. Extracellular traps (ETs) are emerging as potential players in the pathogenesis of lung diseases and are being considered as targets for adjunctive therapies.

Methods: We retrospectively examined Giemsa-stained cytospins of bronchoalveolar lavage (BAL) from children with BE for the presence and prevalence of ETs. To provide insight into the cellular origin of ETs in children with BE, conservative evaluations were made on the white blood cell (WBC) origin of the observed ETs based on cell morphology and staining properties. ETs were categorised into 5 groups: neutrophil ETs (NETs), macrophage ETs (METs), eosinophil ETs (EETs), lymphocyte-like ETs (L-LETs), and ETs of unknown origin (Indeterminant ETs).

Results: ETs were detected in 70 (79%) out of 89 BALs with a median percent ETs per total BAL leukocytes of 0.9% (IQR 0.9-1.5%) and a median total ET count of 3 x 103/mL (IQR 1-7 x 103/mL). Neutrophil ETs (NETs), macrophage ETs (METs) and eosinophil ETs (EETs) were identified in 41%, 65% and 5.7% of BAL samples respectively. A subset of ETs appeared to be of lymphocyte origin (L-LETs), these were present in 10% of BAL samples. The origin of some ETs could not be determined (indeterminate ETs) by microscopic examination of Giemsa-stained BAL cytoslides, these ETs are currently being investigated using immunofluorescent staining.

Conclusions: ETs are present and prevalent in BAL from children with BE and can be detected directly by microscopic examination of Giemsa-stained cytoslides. This presents a cost-effective method that could be used to screen for the presence of ETs in BAL as an adjunct to more specific, and more technically demanding, immunofluorescent ETs staining methods. Further studies to understand pathobiological roles of ETs in the airways of children with BE are warranted.