Deletion of αβ TCR transgenic DP thymocytes by thymic DC. CD4 versus CD8 expression in R1 and R2 of αβ TCR transgenic thymocytes uncultured or cultured for 60 hours alone or with thymic DC isolated from BALB.D2 mice or nontransgenic BALB/c littermate mice. The percentage (large figures) and the absolute number per well (small figures) are indicated for each thymocyte subset. The absolute number of DP and SP thymocytes has been obtained by multiplying the total number of cells per well by the percentage of viable cells, and by the percentage of each thymocyte subset calculated within the total viable cell population. The percentages shown correspond to corrected values, which have been calculated considering DP plus CD4⁺ SP plus CD8⁺ SP equals 100%, ie, excluding DC and DN thymocytes, to allow the direct comparison of the results obtained in different experimental conditions. The percentage of CD4^high SP cells was 50% with BALB.D2 thymic DC and 6% with BALB/c thymic DC. H is CD4^high SP cells; L is CD4^low SP cells. The experiment shown is representative of a series of four experiments with similar results.