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. 2011 Sep 13;9(9):e1001149. doi: 10.1371/journal.pbio.1001149

Figure 1. Superantigen mimetic peptide blocks SEB action and CD28 signaling.

Figure 1

(A, B) p12B (10 µg/ml) inhibits SEB-mediated induction in human PBMC of IL2, IFN-γ, and TNF-α mRNA (autoradiograms) and of protein (graphs; data are shown as means ± SEM (n = 3 experiments)) (A) but not of IL4 and IL10 (B). mRNA was quantitated by RNase protection analysis; β-actin mRNA indicates equal loading of RNA. (C) In SEB structure (pdb3seb.ent), amino acid residues in the 150–161 β-strand(8)/hinge/α-helix(4) domain are shown in purple, with solvent-accessible residues [36] N151, K153, and K154 in orange. Residues contacting MHC-II are colored red; those contacting the TCR are colored green [37]. (D) p12B inhibits induction of IL2 and IFN-γ mRNA in PBMC by αCD28 mAb. PBMC were induced by αCD28 (2.5 µg/ml) alone or with 10 µg/ml p12B. To show that αCD28 does not bind p12B, p12B and CD28-Fc were immobilized and binding of mouse αCD28 was assayed. (E) p12B fails to inhibit induction of IL2, IFN-γ, and TNF-α genes by αCD3. PBMC were incubated with αCD3 (0.1 µg/ml) alone or with 10 µg/ml p12B. mRNA and secreted cytokines were quantitated. (F) p12B inhibits αCD28/αCD3-mediated induction of IL2, IFN-γ, and TNF-α genes but not of IL10. PBMC were incubated with αCD3, αCD28, or both, with or without 10 µg/ml p12B. mRNA and secreted cytokines were determined.