Specificity of the in vitro deletion of TCR Vβ8.1 TG thymocytes. Dot plots show the CD4 versus CD8 profiles (CD4-TC/CD8-FITC staining) of Mtv-7–reactive TCR Vβ8.1 or nonreactive TCR Vβ8.2 thymocytes cultured for 60 hours alone or with B cells fromMtv-7⁺ BALB.D2 or Mtv-7⁻BALB/c mice. Percent deletion values of Vβ8.1 DP thymocytes were 2% and 68% when cultured with BALB/c and BALB.D2 B cells, respectively. For Vβ8.2 DP thymocytes percent deletion value was 0% when either BALB/c or BALB.D2 B cells were used. The absolute cell number per well and the percentage (in boxes) are indicated for each thymocyte subset. The percentages correspond to corrected values, which have been calculated considering DP + CD4⁺SP + CD8⁺SP = 100%. Histograms represent the CD69 expression and FSC profile of DP thymocytes for each culture condition. The percentage of CD69⁺ (FL2 > 20) and blast (FSC > 80) DP thymocytes are shown.