Antigen-specific T lymphocytes must be quantified in order to gauge the quality of an immune response. Typically this is accomplished using cytotoxicity assays or limiting dilution analysis (LDA), but these techniques are lengthy and provide indirect quantitation. Also, LDA cannot count nonproliferative cells. In 1996, Stanford University's Mark Davis developed an alternative strategy that overcomes these problems.1 Davis generated phycoerythrin-conjugated tetramers of human lymphocyte antigen (HLA)-A2 coupled to specific peptides, and used these tetramers to accurately count CD8+ T cells directed against three specific viral peptides by flow cytometry. Stanford has now licensed the technology to Beckman-Coulter Inc. of Fullerton, Calif., which markets it as i·TAg MHC tetramers.

Beckman-Coulter's new San Diego-based Immunomics Operations currently offers a custom tetramer service as well as standard i·TAgs directed against HIV-1 Gag or Pol, and the melanoma MART-1 peptide. For custom tetramers, researchers provide an amino acid sequence and Immunomics synthesizes an...

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