BriefDefinitive Report A -y/b T Cell Receptor Heterodimer Induces the Expression of CD4 and CD8 in Thymocytes

CD4 and CD8 have been useful surface markers for a/R T cell maturation . In an a/(3 T cell receptor (TCR) transgenic SCID mice system, it has been shown that a/0 TCR alone is sufficient to induce CD4 and CD8 surface expression on thymic T cells. Although the late embryonic thymic y/b T cells are predominately single and double positive, it has not been clear if y/b TCR has a similar capacity. In this study, we show that when transgenes encoding the earliest embryonic y/b TCR are coexpressed with the SCID defect, the y/b transgenes promote the appearance of both the CD4 8 and CD4+8+ T cells in the thymus . Furthermore, the expression of CD4 and CD8 does not require continuous surface y/b TCR expression . These results indicate that y/bTCR alone can promote the CD4/8 surface expression, and may suggest a role for y/b T cells in initiating normal thymic ontogeny.