Reduced surface αβ and γδ TCR expression in CD3γ+/−, CD3δ+/−and CD3δ+/leakyindividuals using UCHT-1. αβ T cells were defined as CD8bright and CD4+ in 9 γ +/−, 4 δ+/−, 2 δ+/leaky and 7 +/+ donors. Similar results were obtained with other anti-CD3 mAb (SK7, S4.1, F101.01, data not shown). (A) CD3 MFI ratios (X100) ± SEM relative to controls are shown for the indicated T cell lineages and genotypes. Asterisks in bars indicate significant differences as compared with controls, other comparisons as indicated. p as in Figure 1A. (B) Representative peripheral blood CD3 reactivity patterns of γ+/−, δ+/− or δ+/leaky T cells (dashed lines) as compared with +/+ controls (solid lines). The vertical line in each panel indicates the upper limit of background fluorescence using isotype-matched irrelevant mAb. (C) Intracellular stainings of γ+/− and δ+/leaky T cells (dashed lines) as compared with +/+ controls (solid lines). Vertical lines as in Figure 2B. The numbers in each histogram indicate MFI ratios (x100) relative to controls. (D) Comparative titration of CD3 (UCHT1) binding (MFI) to γ+/− peripheral blood T cells (n = 1) versus +/+ controls (n = 2, mean ± SD). The percentage of bound cells was determined in parallel to establish the endpoint dilution (1:16.000). The arrow indicates the working dilution in all other experiments. Similar results were obtained using other antibodies (F101.01 or BMA031).