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TLR2 Agonist - Heat Killed Bacteroides fragilis
10e9 cells

TLR2 Agonist – Heat-killed Bacteroides Fragilis

HKBF is a heat-killed preparation of nontoxigenic Bacteroides fragilis, a bile-resistant, Gram negative, obligate anaerobe in normal intestinal microbiota.

B. fragilis synthetizes the capsular polysaccharide A (PSA), considered as the archetypical symbiotic immunomodulatory molecule. Indeed, this commensal bacteria impacts immunity at multiple levels. In fetal enterocytes, B. fragilis PSA requires both TLR2 and TLR4 for mediating its anti-inflammatory effects through inhibition of IL-1β [1]. PSA also promotes immune system development in the gut by ensuring a proper Th1/Th2 balance [2]. Moreover, in the adult host, PSA mediates a TLR2-dependent differentiation of IL-10 producing Treg cells and enhances Treg activity directlty through TLR2 [2, 3]. PSA-induced IL-10 confer protection against intestinal inflammation (e.g. colitis) or extra-intestinal inflammation (e.g. experimental autoimmune encephalomyelitis (EAE)) [2]. Outside of the gut, B. fragilis can cause significant pathology, including abscess formation and bacteremia [2,4].

HKBF is a potent stimulator of TLR2 in HEK-Blue™ TLR2 cells.



1. Jiang F. et al., 2017. The symbiotic bacterial surface factor polysaccharide A on Bacteroides fragilis inhibits IL-1β-induced inflammation in human fetal enterocytes via toll receptors 2 and 4. PLoS One. 12(3):e0172738.
2. Erturk-Hasdemir D. and Kasper DL., 2018. Finding a needle in a haystack: Bacteroides fragilis polysaccharide A as the archetypical symbiosis factor. Ann N Y Acad Sci. 1417(1):116-29.  
3. Round JL. et al., 2011. The Toll-like receptor 2 pathway establishes colonization by a commensal of the human microbiota. Science, 332:974-977.
4. Surana NK. And Kasper DL., 2012. The ying yang of bacterial polysaccharides: lessons learned from B. fragilis PSA. Immunological Reviews 245:13-26.



Evaluation of HKBF in HEK-Blue™  hTLR2 and HEK-BlueTM hTLR4 cells
Evaluation of HKBF in HEK-Blue™  hTLR2 and HEK-BlueTM hTLR4 cells

HKBF induces a dose-dependent response in HEK-Blue™ hTLR2 cells. 
HEK-Blue™ hTLR2 and HEK-Blue™ hTLR4 cells were stimulated with increasing concentrations of HKBF. After overnight incubation, the NF-κB response was determined using QUANTI‑Blue™, a SEAP detection reagent, and by reading the optical density (OD) at 655 nm.

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Specificity: TLR2 agonist

Working concentration: 106-107 cells/ml

Solubility: Insoluble (resuspended HKBF results in a cloudy suspension)

Quality Control: 

  • TLR2 activity has been validated using HEK‑Blue™ TLR2 cells.
  • The absence of TLR4 activity has been confirmed using HEK‑Blue™ TLR4 cells.
  • Lack of viability has been confirmed by microbiological testing.
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  • 109 freeze-dried cells of pasteurized nontoxigenic Bacteroides fragilis (HKBF).
    Note: Product was pasteurized by heating to 95 °C.
  • 1.5 ml sterile endotoxin-free water

HKBF is shipped at room temperature

HKBF should be stored at 4 °C. Store resuspended HKBF at -20°C.

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