What is the most common reason for no signal in ELISA?
Mishandling the recombinant cytokine standard; primarily by diluting this in PBS or water without a protein carrier (causing adsorption to the polystyrene or polypropylene walls) or secondarily by reducing amount of carrier protein stabilizer for freeze/thaw. Aliquoting in too small of a volume (e.g., <20 ul) is also suspected to contribute to poor stability for freezing.
