Conditional expression of ITK-SYK in T cells induces a lymphoproliferative disease. (A) Peripheral blood samples from ITK-SYK^CD4-Cre (starting with n = 19) and ITK-SYK^CD19-Cre mice (n = 8) were obtained at the indicated time points. The frequencies of eGFP fluorescent lymphocytes in individual animals were determined by FACS analysis. The total number of ITK-SYK^CD4-Cre mice declined over time as a result of disease-related mortality. Horizontal bars indicate the means. (B) Kaplan-Meier curve of ITK-SYK^CD4-Cre (n = 73) and control (CD4-Cre) mice (n = 15). (C) Macroscopic appearance of representative spleens from 20-wk-old control and ITK-SYK^CD4-Cre mice are shown (in centimeters). (D) Splenocytes from 20-wk-old control and ITK-SYK^CD4-Cre mice were stained with antibodies against TCR-β. The frequency of eGFP–expressing T cells in a diseased ITK-SYK^CD4-Cre mouse is indicated. Data shown in C and D are representative of a total number of 20 mice per genotype analyzed.