Lipocalin-2 functions as inhibitor of innate resistance to mycobacterium tuberculosis

Sara Louise Dahl, Joshua S. Woodworth, Christian Johann Lerche, Elisabeth Præstekjær Cramer, Pia Rude Nielsen, Claus Moser, Allan Randrup Thomsen, Niels Borregaard, Jack Bernard Cowland*

*Corresponding author for this work
9 Citations (Scopus)
50 Downloads (Pure)

Abstract

Lipocalin-2 is a constituent of the neutrophil secondary granules and is expressed de novo by macrophages and epithelium in response to inflammation. Lipocalin-2 acts in a bacteriostatic fashion by binding iron-loaded siderophores required for bacterial growth. Mycobacterium tuberculosis (M.tb) produces siderophores that can be bound by lipocalin-2. The impact of lipocalin-2 in the innate immune response toward extracellular bacteria has been established whereas the effect on intracellular bacteria, such as M.tb, is less well-described. Here we show that lipocalin-2 surprisingly confers a growth advantage on M.tb in the early stages of infection (3 weeks post-challenge). Using mixed bone marrow chimeras, we demonstrate that lipocalin-2 derived from granulocytes, but not from epithelia and macrophages, leads to increased susceptibility to M.tb infection. In contrast, lipocalin-2 is not observed to promote mycobacterial growth at later stages of M.tb infection. We demonstrate co-localization of granulocytes and mycobacteria within the nascent granulomas at week 3 post-challenge, but not in the consolidated granulomas at week 5. We hypothesize that neutrophil-derived lipocalin-2 acts to supply a source of iron to M.tb in infected macrophages within the immature granuloma, thereby facilitating mycobacterial growth.

Original languageEnglish
Article number02717
JournalFrontiers in Immunology
Volume9
Number of pages16
ISSN1664-3224
DOIs
Publication statusPublished - 26 Nov 2018

Keywords

  • 24p3
  • innate immunity
  • iron metabolism
  • Lcn2
  • Mycobacterium tuberculosis
  • neutrophils
  • NGAL

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