Immune cells and their mediators are key players in human cancer progression involving alternation in the number and function of immune cells, both peripheral and at the site of tumor. Through reliable predictive biomarkers, cancer can be predicted, and progression and response to therapy followed. Thereby immune biomarkers, e.g., cytokines and chemokines can serve as intermediate mediators of cancer diagnostics. Multiplex analysis of immune mediators in small blood volumes allows for rapid quantification of large number of circulating analytes. The fluorochrome (Luminex) technique is a bead-based sandwich immunoassay that combines the enzyme-linked immunosorbent assay (ELISA) with flow cytometry. The Luminex technique allows multiple immune mediators to be measured simultaneously in small volumes, and provides a convenient and sensitive tool for the detection of a large number of extracellular secreted cytokines and chemokines to be used in prediction and therapy prognosis of cancer.

The technique is based on so-called microspheres (beads) that serve as a solid phase for molecular detection. These individually dyed microbeads have monoclonal antibodies directed against the cyto- and chemokines of interest and allow a simultaneous detection of up to nearly 100 cyto- and chemokines in a dual-laser flow analyzer. Immune mediators can be detected in serum and plasma samples as well as in cell culture supernatants from in vitro stimulated peripheral blood mononuclear cells (PBMC). This chapter describes the Luminex technique for detection of immune mediators in cancer by using magnetic bead sandwich immunoassay, with focus on some important pre-analytic factors, e.g., cell separation and cryopreservation and thawing of PBMC that may affect the outcome of detection of immune mediators. The Luminex technique thus represents a very suitable method to identify immune mediators in cancer tissues in order to diagnose and improve clinical outcome of cancer.