PD-1 does not recruit SHP1 even in SHP2-deficient T cells. (A) Left: Cartoons illustrating Raji-Jurkat co-culture assays in which SHP2 KO Jurkat (PD-1–mGFP⁺) or Jurkat (BTLA-mGFP⁺) cells were stimulated with SEE-pulsed Raji (PD-L1–mCherry⁺) or Raji (HVEM-mRuby⁺) cells. Right: Representative IBs of phosphotyrosine (pY IB) and GFP (GFP IB) of PD-1–mGFP or BTLA-mGFP IP (GFP IP) and the coprecipitated SHP1 from the indicated co-culture lysates, with the duration of stimulation before lysis indicated (see Materials and methods). (B) Same as A, except SHP2 KO Raji (PD-L1–mCherry⁺) cells or SHP2 KO Raji (HVEM-mRuby⁺) cells were used. (C) Jurkat-PLB assays showing the degree of recruitment of SHP1 or SHP2 to PD-1 microclusters. Left: Cartoons depicting the indicated type of Jurkat cell interacting with a PLB containing OKT3 and PD-L1. Middle: Representative TIRF images of the indicated channels. Scale bars, 5 µm. Right: Plots showing fold intensities of the indicated channels along the yellow diagonal line in the overlaid images (see Materials and methods).