Thy1 retroviral reporters: a versatile platform for congenic background-independent adoptive transfer and CD8+ T cell differentiation studies.

Adoptive T cell transfer remains a fundamental technique for dissecting the molecular mechanisms governing T cell differentiation. A successful adoptive-transfer experiment typically relies on labor-intensive construction of specific congenic mouse strains to distinguish donor from host cells. This limitation may be addressed by a readily detectable surface reporter. Thy1 is a candidate, but it remains unclear whether it is a reliable reporter for monitoring adoptively transferred CD8+ T cell differentiation because Thy1 is a functional protein involved in thymic development and cell activation. To address this question, we systematically evaluated the reliability, stability, and functional neutrality of Thy1.1 and Thy1.2, two Thy1 isoforms, as adoptive-transfer reporters during CD8+ T cell differentiation in vivo. Our results show that endogenous Thy1 expression remains stable across the differentiation stages examined. In the experimental settings tested, exogenous Thy1 reporter expression did not measurably alter the assessed differentiation phenotypes or donor-cell recovery. We further constructed and validated a Thy1 reporter-based platform that captured phenotypes associated with both loss-of-function (shRNA) and gain-of-function (cDNA) modulation of the transcription factor T-bet. This system provides a practical option for congenic background-independent adoptive transfer and genetic studies of CD8+ T cell differentiation.