Hi Tom. Depends on the species. In cows, everything from 1- to 100 μg ml−1 of poly(I:C) seems to work well, in dogs 1000ng ml-1 have been used. So, there is a wide range you can test. ABSOLUTELY crucial: test your ploy(I:C) for LPS contamination, esp if you do whole blood assay. Dont use anything which is not considered LPS free (i.e. less than ).01 EU/ml). Hope that helps.

Hi Dirk. Thanks for your response. I am looking to do it in humans. I have noticed that the majority of papers using whole blood stimulation seem to be using animals, and from what you say it would be difficult to infer too much from the concentrations used in these studies. If possible I would do a dose response experiment first but it is a fairly unique set of samples, so that won't be possible.

Thanks again.

We have used 50 ug ml-1 for human whole blood, and that worked well. But have a look into PubMed, and pick the concentration most often used? Again: I cant stress enough the LPS contamination issue. Initially, we bough poly(I:C) from Sigma, they had no idea regarding the LPS content, and when we tested....well, it wasnt clear where the response in the blood came from. Invivogen is a good starting source.

My colleagues have also used poly I:C from Invivogen and said that it worked well for their cell culture experiments. I am actually planning to use LPS as a separate stimulus, however there seems to be more to go on in the literature for stimulation protocols and I am struggling to find much that fits my experimental design when using Poly I:C.

I am concerned that I may stimulate my samples and then the response will be outside of the dynamic range of the ELISA kits that I have.

I am not sure about poly I:C but when we ex-vivo testing of antibodies we were very concerned about contaminating LPS. So, we titered LPS in our ex-vivo assays. We saw quite a number of cytokines go up significantly, even at doses of LPS well below the allowable limit for IV drugs. It made analyzing the responses due to the antibodies quite messy.