Multiplexed microsphere-based flow cytometric immunoassays for human cytokines.

Cytokines play a pivotal role in the regulation of immunologic, hematologic and wound-healing processes. They function to stimulate as well as inhibit the proliferation, differentiation and maturation of a variety of cell types. Thus, their functions are pleiotropic as well as interdependent to the extent that any cytokine may have effects that are synergistic or antagonistic with other cytokines. Cytokines also display redundancy when one mimics the functions of others. These characteristics imply that measuring the levels of one cytokine in a biologic system provides only a fraction of the information that is relevant to the existing physiologic state. A more realistic indication of the complexity of cellular interactions would include measurements of multiple cytokines at any time point. One method of multiplexed analysis can be performed by capture of the cytokines on an array of fluorescent microspheres for quantitation by flow cytometry. This technology has been applied to a variety of biomolecules, but simultaneous quantitation of multiple cytokines in a small sample volume has become rapid, inexpensive, reliable and informative.