So you're trying to Analyse chemokines which were secreted into the medium by the cells, if I understand correctly? As chemokines are Proteins, qPCR would be useless for secreted chemokines in the supernatant.

I personally would collect the supernatant and then perfom an ELISA (if there is an ELISA available for your Protein of interest). ELISA is more sensitve and less time-consuming than Western Blot (usually you also need to optimize your WB protocol quite a lot).

Hope this helps :-)

Espression dose not necessarily mean production in the supernatant especially in vitro. However, if you Know  that it is so, the eas

Great question and so important.

As both Lukas and GJM have said above, mRNA transcriptome expression is molecularly nice, but then subjected to vagaries of RNA stability, secretion/degradation etc. If you go this route: forget qPCR and find a facility nearby that can RNA -SEQuence directly (eg using Illumina technology).

The most efficient way to study cytokine protein secreted into supernatant, is some multiplex technique. Multplexes typically improve over ELISAs and Western Blot is your last resort.  I use multi well multi plexes because I typically want to know >12-20 cytokines at one shot from a limited sample. The problem is dynamic range as some are in fmol/ml while others are in nmol/ml.  I am unhappy with BIORad bead multiplex, because it is log-log calibration, prone to too much error.

 This is specialized business where calibration issues will eat you alive. Consider professional companies like Ray Biotech and Mesoscale.

Two ways to go:

1) Collect supernatant from cell culture, spin (300g if using a microfuge) to remove any cell debris and transfer the supernatant to a separate tube. Use a suitable ELISA kit for the chemokine of your interest.

2) Although Chemokine is a secreted protein and ELISA is the simplest and faster way to measure it, you can still be able to see a differential mRNA expression if you extract RNA from the cells and do Real-time PCR or regular PCR.  You may use Trizol (Invitrogen) for RNA extraction, and superscript II to make cDNA for PCR. If you do Real-time PCR (best), buy or design  your chemokine specific primer set and SYBR green master mix.  If you don't have a Realtime PCR machine, use regular quantitative PCR, pause machine to collect equal amount of aliquot from each sample at 30, 35 and 40 cycles and run the samples in 1% Agarose gel. 

If you are looking at expression, I would use ELISA so you don't miss secreted chemokines and Western Blot to check protein expression from protein within your cells.  While RNA expression can be quantified, it will not tell you whether or not the actual protein has been transcribed.