Hi Guys,
I new to immunology and I have a simple question about LPS stimulation on BMDMs, also known as 'LPS priming'.
I read something that says LPS binding to TLR4 needs LPS binding protein(LBP). And many studies are actually targeting this LBP to treat sepsis. I understand that in a physiological condition, there should be LBP in the blood. However, in cell culture, what are the sources of this LBP? If you add LPS directly (without adding LBP) to BMDMs, will it activate inflammatory gene expression?
Thank you in advance!
Xingchen
Hi Xingchen Dong,
We use MoDC and LPS works very well without LBP, but our Medium contains FCS. I don´t know if it works if you use any serum-free medium.
Jochem
LBP isn't necessary to LPS activation of TLR-4. LBP activity is LPS concentration dependent. LBP is mostly produced by the liver (I'm not sure if activated macrophages/DCs can also produce it... never looked at it).
As for whether LPS can stimulate in serum free medium... yes it can.
Hi,
LBP is probably required to extract LPS from the bacterial cell membrane. In case of free LPS, it could directly find its way to CD14 which then transfers the LPS to TLR4-MD-2 complex.
Sudeep Kumar Shen-An Hwang So, there is no point of blocking LPS-LBP interaction in vitro since LPS can activate macrophages regardless of the presence of LBP? What about in vivo? Do you guys think LBP in circulation is necessary for LPS induced cytokine production, or"cytokine storm"?
Thank you guys.
Yes, no point in vitro.
The action of LBP is LPS dependent. It is NOT necessary for LPS sepsis, but it can enhance it. And there are reports that LBP when at a high enough conentration can inhibit LPS signaling...
The major receptor for LPS is TLR4-MD-2 complex and the way it works is that 5 of the six lipid chains are buried inside the MD2 and the sixth one bridges the othe TLR4 for dimerization. So, you get a dimer of TLR4-MD2, and the down-stream signalling ensues.
There are pharmacological agents resembling LPS but only with 4 or 5 lipid chains, which acts as an antagonist of LPS signalling. Thus, if you want to inhibit the effect of LPS then the best way is to target the interaction between LPS and TLR4-MD2 complex.
LPS need TLR-4 and CD14 and PB for active signalitation way, and it going up NG-kB and IL
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