BFP characterization of surface-expressed TCRαβ or preTCR. (A–D) SCID.adh parental cell line lacking TCRα and -β was retrovirally transduced with either N15αβ or the indicated β and assayed by FACS using anti-TCR antibody H57. (A) N15αβ, N15β WT, and SCID.adh parental. (B) N15β WT, N15β M22, N15β M23, and SCID.adh. (C) N30β WT, N30β M12, and SCID.adh. (D) N15β MP3 and SCID.adh. (E) SCID.adh parental cell line lacking TCRα and -β showed no adhesion when probed with VSV8/Kb using 0.1- and 1-s contact times. (F) Force lifetime curves for N15β WT vs. MP3 show maximal lifetime at a lower force for MP3. WT data are from Fig. 3 D and E for comparison.