Figure 7.

Transgenic T cells expressing a productive second TCR are more likely to become CD4⁺. (A) TCRα and TCRβ usage of HLA-A2/MART1-reactive TCRs repeatedly identified by single cell TCR sequencing. The transgenic TCR is the DMF5 clone introduced by lentiviral transduction; while the expanded non-transgenic TCR was from a Tet-binding CD4⁺ T cell clone, identified three times in a sample of 23 cells. CDR3 homology that might contribute to similar binding to MART1 Tet is underlined. (B) Percentage of cells expressing the transgenic TCR (clone DMF5) or a non-transgenic TCR in sorted T cell populations. (C) Percentage of cells with transgenic TCR that express a productive second TCRα, a non-productive second TCRα, or had no second TCRα detected (the last two equivalent to single TCR). Lack of two productive TCRβ was used to exclude the possibility of having two T cells in the same well. The efficiency of TCR amplification was somehow low in Tet⁺ CD8⁺ T cells (11/24), but high in other subsets: Tet⁺ CD4⁺ CD25⁺ CD127⁻ (23/23), Tet⁺ CD4⁺ CD25⁻ CD127⁺ (24/24), Tet-CD8⁺ (10/12), and Tet⁻ CD4⁺ (12/12). The few Tet⁺ cells that were not TCR-transgenic were not included in this analysis as to not confound the results. 4 + R, CD4⁺ CD25⁺ CD27⁻ (regulatory); 4 + C, CD4⁺ CD25⁻ CD127⁺ (conventional).