Peptide Antigen Concentration Modulates Digital NFAT1 Activation in Primary Mouse Naive CD8

Area of Science:

• Immunology
• Cellular Biology
• Molecular Biology

Background:

• Naive T cells are quiescent until activated by antigen-presenting cells (APCs) via the T cell receptor (TCR).
• TCR signaling initiates rapid transcriptional changes crucial for T cell differentiation into effector or memory cells.
• Understanding the precise mechanisms of TCR signaling activation is key to T cell fate determination.

Purpose of the Study:

• To develop and validate a novel method for analyzing TCR signaling pathway activation in primary mouse naive T cells.
• To investigate the digital activation patterns of the NFAT1 transcription factor in response to natural antigen stimulation.
• To elucidate how T cells discriminate varying levels of antigen availability.

Main Methods:

• Isolation of nuclei from primary mouse naive T cells co-cultured with APCs presenting natural peptide antigens.
• Utilizing cell tracking dyes for distinguishing CD8+ T cell nuclei from APC nuclei via flow cytometry.
• Quantifying NFAT1 transcription factor translocation as a readout of TCR signaling activation.

Main Results:

• Demonstrated clear digital activation of NFAT1 in OT-I T cells stimulated with OVA peptide presented by splenocytes.
• Showed that OVA concentration precisely controls the fraction of cells activating NFAT1, indicating a signaling threshold.
• Observed that this activation is cell-contact dependent and more precise than responses to ionomycin stimulation.

Conclusions:

• The novel coculture nuclei isolation protocol is effective for studying stimulation-dependent protein translocation in lymphocytes.
• TCR signaling exhibits digital behavior, requiring a distinct threshold to activate NFAT1 in naive T cells.
• This digital response mechanism may enable T cells to accurately sense antigen concentration during infections.