Detecting interferon-gamma release from human CD4 T-cells using surface plasmon resonance

Cytokine secretion by leukocytes is an important indicator of immune response to pathogens and therefore has significant implications in disease diagnostics. Given heterogeneity of leukocyte subsets and the ability of multiple cell subsets to secrete the same cytokines, connecting cytokine production to a specific leukocyte subset is a distinct challenge. In the present paper we describe a strategy combining antibody (Ab)-based affinity cell separation and surface plasmon resonance (SPR) for capturing human CD4 T-cells and for label-free detection of cell-secreted interferon (IFN)-gamma--an important inflammatory cytokine. Human blood was introduced into a flow chamber modified with anti-CD4 Abs resulting in capture of CD4(+) T-cells. After mitogenic activation of cells inside the flow chamber, culture medium was routed onto an SPR chip modified with monoclonal IFN-gamma Abs. SPR signal observed in this experiment correlated with cytokine production by T-cells. The strategy of combining SPR detection with cell purification may be used in the future for label-free, sensitive detection of multiple cytokines or proteins secreted by the desired cell subset.