Homogeneous assays allow direct "in well" cytokine level quantification.

We have developed several homogeneous cytokine assays based on TR-FRET using europium cryptate- and cross-linked allophycocyanin-conjugated antibodies. Taking advantage of homogeneous assays, we have coincubated the cells with the antibody pair during the stimulation step. The results show that the presence of cells in wells at the time of reading does not alter the results. Furthermore, this experimental procedure avoids cumbersome transfer and storage steps streamlining sample analysis. Finally, it facilitates the follow-up of cytokine production.