Quantifying MHC dextramer-induced NFAT activation in antigen-specific T cells as a functional response parameter

Area of Science:

• Immunology
• Cellular Immunology
• T cell biology

Background:

• Major histocompatibility complex (MHC)-multimers detect antigen-specific T cells (ASTs) by mimicking T cell receptor (TCR) recognition of peptide-MHC complexes.
• Cytotoxic CD8 T cells utilize TCRs to identify specific antigens presented by MHC molecules.

Purpose of the Study:

• To investigate if TCR engagement by MHC-multimers is sufficient to elicit a functional T cell response.
• To assess the activation of the NFAT signal transduction cascade upon binding of cytomegalovirus (CMV)-specific dextramers to CMV-ASTs in bone marrow transplant recipients.

Main Methods:

• Quantified NFAT activation by measuring nuclear translocation of NFAT1 in CD8+ CMV-ASTs (CASTs) and CD8+ non-CASTs using imaging flow cytometry.
• Assessed downstream functional responses, including interferon gamma production.
• Optimized parameters for dextramer-induced NFAT activation, including sample preparation, temperature, and exposure duration.

Main Results:

• CMV-dextramer binding induced NFAT1 nuclear localization in CASTs within 10 minutes, correlating with interferon gamma production.
• Optimal conditions for dextramer-induced NFAT activation were 2-hour exposure in whole blood at room temperature.
• Observed intra- and inter-individual heterogeneity in NFAT activation among CASTs; no activation was seen in non-CASTs.

Conclusions:

• Binding of antigen-specific dextramers to ASTs specifically activates NFAT, correlating with downstream functional responses.
• The observed heterogeneity in NFAT activation suggests that AST enumeration alone may not fully represent an individual's immune status.
• Functional assessment via NFAT activation provides deeper insights into T cell responsiveness against specific antigens.