Endosomal recognition of Lactococcus lactis G121 and its RNA by dendritic cells is key to its allergy-protective effects

Karina Stein, Stephanie Brand, André Jenckel, Anna Sigmund, Zhijian James Chen, Carsten J. Kirschning, Marion Kauth, Holger Heine

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Background Bacterial cowshed isolates are allergy protective in mice; however, the underlying mechanisms are largely unknown. We examined the ability of Lactococcus lactis G121 to prevent allergic inflammatory reactions. Objective We sought to identify the ligands and pattern recognition receptors through which L lactis G121 confers allergy protection. Methods L lactis G121–induced cytokine release and surface expression of costimulatory molecules by untreated or inhibitor-treated (bafilomycin and cytochalasin D) human monocyte-derived dendritic cells (moDCs), bone marrow–derived mouse dendritic cells (BMDCs), and moDC/naive CD4+ T-cell cocultures were analyzed by using ELISA and flow cytometry. The pathology of ovalbumin-induced acute allergic airway inflammation after adoptive transfer of BMDCs was examined by means of microscopy. Results L lactis G121–treated murine BMDCs and human moDCs released TH1-polarizing cytokines and induced TH1 T cells. Inhibiting phagocytosis and endosomal acidification in BMDCs or moDCs impaired the release of TH1-polarizing cytokines, costimulatory molecule expression, and T-cell activation on L lactis G121 challenge. In vivo allergy protection mediated by L lactis G121 was dependent on endosomal acidification in dendritic cells (DCs). Toll-like receptor (Tlr) 13−/− BMDCs showed a weak response to L lactis G121 and were unresponsive to its RNA. The TH1-polarizing activity of L lactis G121–treated human DCs was blocked by TLR8-specific inhibitors, mediated by L lactis G121 RNA, and synergistically enhanced by activation of nucleotide-binding oligomerization domain-containing protein (NOD) 2. Conclusion Bacterial RNA is the main driver of L lactis G121–mediated protection against experimentally induced allergy and requires both bacterial uptake by DCs and endosomal acidification. In mice L lactis G121 RNA signals through TLR13; however, the most likely intracellular receptor in human subjects is TLR8.

Original languageEnglish (US)
Pages (from-to)667-678.e5
JournalJournal of Allergy and Clinical Immunology
Issue number2
StatePublished - Feb 1 2017


  • Allergy protection
  • Lactococcus lactis G121
  • Toll-like receptor 13
  • Toll-like receptor 8
  • bacterial RNA
  • dendritic cells
  • endosomal acidification
  • pattern recognition receptor

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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