Naive T-cell proliferation and expansion in mice deficient in TCRβ/δ. Ly5.1 naive T cells (10⁶) were adoptively transferred into TCRβ^−/− and TCRβ/δ^−/− recipients. The FACS profiles, the ratio, and the total cell recovery of donor CD4 and CD8 T cells were analyzed 7 days after transfer. Each symbol represents individual mice. *P < .05; **P < .01.