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

Figure 6. Mutation of SEB β-strand(8)/hinge/α-helix(4) domain affects binding to CD28, Th1 cytokine gene induction and lethality.

Figure 6

(A) Induction of cytokine genes by wt and tk2 mutant SEB. PBMC were induced with 1 ng/ml wt or tk2 SEB; mRNA (autoradiograms) and secreted cytokines (graphs; data are shown as means ± SEM (n = 3)) are depicted. (B) Lack of lethality of tk2 SEB. Mice (n = 5 per group) were challenged with 10 µg wt or tk2 SEB; p for survival, 10−5. (C) Affinity of tk2 SEB for CD28. Representative SPR responses for binding of wt and tk2 SEB to immobilized CD28-Fc, p1TA, and p2TA are shown for 5 µM wt and tk2 SEB or RNase A to facilitate comparison; kinetic data were collected for five 2-fold increments in protein concentration from 1.25 µM (Table S2). (D) Dominant-negative phenotype of tk2 SEB. PBMC were induced with 1 ng/ml wt SEB, 0.1 ng/ml tk2 SEB, or both; secreted cytokines were determined as shown (data are shown as means ± SEM (n = 3)).