Analysis of thymocytes from chimeric mice bearing GPI⁻ cells. (A) Thymocytes were stained in four colors for Ly5.1, CD4, CD8, and Thy1. CD4⁺ and CD4⁻ cells were separately examined for the expression of CD8 and Thy1. (B) The selected CD4,CD8 double negative thymocytes were further stained in four colors for Ly5.1, CD44, CD25, and Thy1. CD25⁺ and CD25⁻ cells were separately examined for the expression of CD44 and Thy1.