The recommendation is to do a dilution series whenever you are implementing a new ELISA/when using a new experimental setup. Hence, the lack of that info in protocols/technical sheets. Cytokine levels would depend on your experimental setup, health status of your subjects and any treatment that they have undergone. If you are using naïve samples from healthy subjects, you should start with undiluted/neat samples. If you expect your samples to have IL-6, try starting with 1:10. If these subjects have inflammatory conditions/sepsis, try using higher dilutions like 1:100 or 1:1000 as your starting dilution.

Thanks Julie

I've spent al afternoon looking for this information on the company website and every single article says " assay done according to manufacturer's instruction. The company couldn't help me out as it's a developmental assay. One last question....if I'm uisng 1:1 or 1:10 could you recomend a % blocker for me please?

I know what you mean; I used to use the same language in my publications. All it means is that the assay followed the procedure that the manufacturer recommends. That doesn't include sample dilutions. The same applies to the blocking buffer. Depending on your analyte, you may have to try several before you find the one that works for you. I am linking a resource below which you can use as a starting point. To make sample dilutions, use the dilution buffer thag the kit recommends (Reagent Diluent: (Catalog # DY995), or 1% BSA in PBS, pH 7.2-7.4, 0.2 µm filtered).

https://info.gbiosciences.com/blog/elisa-blocking-agents-blocking-solutions

That's great Julie, I'll try BSA and if needed I find non-fat dried milk has worked well in the past. Many thanks!