The pre-TCR cooperative role in TEL-JAK2 leukemogenesis cannot be replaced by TCRαβ expression and it does not require PKCθ. (A) Cell surface immunostaining of one TEL-JAK2/Ptcra^+/− (no. 75) and 6 TEL-JAK2/Ptcra^−/− (nos. 42, 61, 63, 66, 87, and 88) representative tumor cases using antibodies against CD25 and TCRβ or an isotypic control antibody. (B) Thymus, spleen, and lymph node weights were plotted for Ptcra^+/− (n = 7) and Ptcra^−/− TEL-JAK2 transgenic mice showing CD8⁺ T-cell leukemia containing a low (n = 3) or high (n = 5) percentage of TCRβ⁺ cells. NS indicates not significant; *P < .05; **P < .01; ***P < .001 (unpaired t test). Average organ weight is indicated by horizontal bars. (C) Kaplan-Meier leukemia-free survival curves for EμSRα-TEL-JAK2 transgenic mice deficient or not for Prkcq show no statistically significant differences. The number of mice in each group is given in parentheses.