Figure 10. Phosphorylation of SHP-1 Ser⁵⁵⁷ is critical for T cell development.

(a,b) DPK cells expressing vector alone (Mock) or mutant SHP-1 (SHP-1^S557A) were stimulated with the indicated concentrations of PCC peptides presented on DCEK cells expressing I–E^k. The percentages of CD4 SP thymocytes (a) and CD5⁺ cells in DP thymocytes (b) at day 3 were analysed by flow cytometry. *P<0.05, **P<0.01. (c) Targeting construct for establishment of SHP-1^S557A knock-in mice. (d) Phosphorylation and expression level of SHP-1 in unstimulated- and TCR-stimulated-WT and SHP-1^S557A/S557A thymocytes were examined by Phos-tag immunoblot analysis (upper panel) and Western blot analysis (lower panel). (e) Analysis of CD4 SP cell generation in thymocytes expressing phosphorylation-defective SHP-1^S557A. CD3ɛ^Δ5/Δ5 mice that were transferred with mixed BM cells from CD45.1⁺ WT and CD45.2⁺ SHP-1^S557A/S557A mice were analysed for CD4 and CD8 expression on thymocytes by flow cytometry 4 weeks after BMT. Data are presented as mean±s.d. of triplicate assays (a,b) and representative of three (a,b), two (d) or five (e) independent experiments. Unpaired two-tailed Student's t test is used to calculate P values.