Estimating the precursor frequency of naive antigen-specific CD8 T cells

Area of Science:

• Immunology
• T cell biology
• Viral immunology

Background:

• The frequency of naive T cells specific for any given antigen is below direct measurement limits.
• Estimating precursor frequency is crucial for understanding immune responses.
• Lymphocyte repertoire diversity poses challenges for direct precursor frequency measurement.

Purpose of the Study:

• To estimate the precursor frequency of naive CD8 T cells specific for the LCMV GP33-41 epitope.
• To quantify the expansion and memory formation of these cells after Lymphocoria choroiditis (LCMV) infection.

Main Methods:

• Adoptive transfer of T cell receptor transgenic cells into syngeneic recipients.
• Titration of antigen-specific cells to determine precursor frequency.
• Quantification of T cell expansion and memory pool generation post-LCMV infection.

Main Results:

• The precursor frequency of naive CD8 T cells specific for the H-2D(b)-restricted GP33-41 epitope of LCMV was estimated to be 1 in 2 x 10(5).
• In uninfected mice, there are approximately 100-200 epitope-specific naive CD8 T cells.
• LCMV infection leads to a >1,000-fold increase in epitope-specific CD8 T cells, generating a memory pool of approximately 5 x 10(5) cells.

Conclusions:

• Adoptive transfer methods can accurately estimate rare T cell precursor frequencies.
• A small number of naive CD8 T cells can generate a substantial effector and memory population upon viral challenge.
• This study provides quantitative insights into CD8 T cell repertoire dynamics during viral infections.