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Rapid identification of antigenic T-cell epitopes by extracellular acidification rate signals.

We used a silicon-based biosensor, a microphysiometer, to measure real-time extracellular acidification rate signals associated with T lymphocyte responses to peptide ligands interacting with the T-cell receptor (TCR). We compared these effector responses with those of interferon-gamma (IFN-gamma) production, and T-cell proliferation. Within minutes, major histocompatibility complex (MHC)-bound peptides on antigen-presenting cells (APCs) engaged the TCR to increase acidification rates of the extracellular media was measured by microphysiometer. We exposed two myelin peptide-specific human T-cell clones, MSF132E11 (DRB1*1501 restricted) and TOM3A6 (DRB5*0101 restricted), to truncated analogues of the parent MBP 84-102 peptide, in the presence of MHC restricted human antigen-presenting cells, and measured the extracellular acidification rate signal changes, IFN-gamma production and T-cell proliferation. The core epitopes recognized by these clones were identified by microphysiometer and found to be MBP 88-100 and MBP 91-100, respectively. These epitopes were identical to those identified by the IFN-gamma and proliferation assays. We conclude that measurement of real-time extracellular acidification rate signals by the microphysiometer may facilitate rapid identification of human T-cell epitopes involved in immune disorders and the development of specific T-cell antagonists.