Fig. 5

B7-1 and B7-2 dimer interface mimetic peptides attenuate engagement of CD28 by the cognate B7 costimulatory receptor. A In cartoon model of the extracellular domain of costimulatory receptor B7-1 (CD80) (green; 1dr9.pdb), a double beta-barrel, amino acid residues forming pB1-8 are modeled in sticks, with 2 residues making homodimer interface contacts shown in yellow. B, C pB1-8 selectively attenuates intercellular B7-1/CD28 engagement (B) but not B7-2/CD28 engagement (C). Receptor engagement was assayed by flow cytometry as in Fig. 3K for B7-1/CD28 engagement and as in Fig. 3D for B7-2/CD28 engagement. D In the extracellular domain of B7-1, amino acid residues forming pB1-78 are modeled in sticks, with 4 residues making homodimer interface contacts shown in yellow and orange. E, F pB1-78 selectively attenuates intercellular B7-1/CD28 engagement (E) but not B7-2/CD28 engagement (F). G, H pB2-7 selectively attenuates intercellular B7-2/CD28 engagement (H) but not B7-1/CD28 engagement (G). Data are mean and SEM of three independent experiments (contour plots: Additional file 1: Fig. S6). Intercellular receptor engagement was compared using the one-tailed unpaired student’s t-test; *p < 0.05, **p < 0.005, ***p < 0.001, ****p < 0.0001; n.s, not significant