Fig 1: MHC class II molecules are dispensable for SEB-induced inflammatory cytokine production in human primary CD4+ and CD8+ T cells. (A, B) Human CD4+ T cells (A) or CD8+ T cells (B) were isolated from the peripheral blood of healthy donors (HD). One representative FACS analysis of human CD4+ T cells stained with anti-CD4-PE plus anti-CD28-FITC or anti-B7.1-FITC or anti-B7.2-FITC or anti-CD4-FITC plus anti-HLA-DR-APC (A), or human CD8+ T cells stained with anti-CD8-APC plus anti-CD28-FITC, or anti-B7.1-FITC, or anti-B7.2-FITC, or anti-CD8-FITC plus anti-HLA-DR-APC (B). Numbers within each quadrant indicate the percentage of positive cells. (C) The percentage of human CD4+ T cells or CD8+ T cells from HD (n = 5) expressing B7.1, B7.2, HLA-DR and CD28 were calculated. The results express the mean percentage of positive cells ± SEM. Statistical significance was calculated by Student’s t test. Mean percentage values: CD4+, B7.1 = 0.5, B7.2 = 4.6, HLA-DR = 3.5, CD28 = 93.8; CD8+, B7.1 = 0.2, B7.2 = 2.5, HLA-DR = 4.3, CD28 = 73. (D–I) CD4+ (D–I) or CD8+ T cells (D–F) from HD were cultured for 24 hours with medium (Med), or in the presence of Dap3/B7 cells (D–I) or 5-3.1/B7 cells (G–I) with or without 1 μg ml-1 SEB. IL-2 (D), IFN-γ (E) and TNF levels (F) in culture supernatants were measured by ELISA. Data show the mean ± SEM. Statistical significance was calculated by the Mann-Whitney test. Mean values: (D–F) (n = 5) IL-2 CD4+, Med = 0.5 pg ml-1, B7 = 12.7 pg ml-1, B7 SEB = 1902 pg ml-1; IL-2 CD8+, Med = 0 pg ml-1, B7 = 173.4 pg ml-1, B7 SEB = 1320 pg ml-1; IFN-γ CD4+, Med = 0 pg ml-1, B7 = 0 pg ml-1, B7 SEB = 858.4 pg ml-1; IFN-γ CD8+, Med = 0 pg ml-1, B7 = 4.9 pg ml-1, B7 SEB = 1240 pg ml-1; TNF CD4+, Med = 24.8 pg ml-1, B7 = 19.4 pg ml-1, B7 SEB = 1664 pg ml-1; TNF CD8+, Med = 5.2 pg ml-1, B7 = 19.4 pg ml-1, B7 SEB = 1315 pg ml-1; (G–I) CD4+ T cells (n = 4), IL-2, Med = 0 pg ml-1, Dap3/B7 = 0 pg ml-1, Dap3/B7 SEB = 6036 pg ml-1, 5-3.1/B7 = 4.04 pg ml-1, 5-3.1/B7 SEB = 1006; IFN-g, Med = 1.1 pg ml-1, Dap3/B7 = 3.7 pg ml-1, Dap3/B7 SEB = 1676 pg ml-1, 5-3.1/B7 = 21.2 pg ml-1, 5-3.1/B7 SEB = 1935; TNF, Med = 8.9 pg ml-1, Dap3/B7 = 32.8 pg ml-1, Dap3/B7 SEB = 4592 pg ml-1, 5-3.1/B7 = 66.5 pg ml-1, 5-3.1/B7 SEB = 6920. (*) p < 0.05, (**) p < 0.01, (****) p < 0.0001. NS, not significant.