Specific CD28 blockade reduces human and rat T-cell proliferation in primary MLR.
(A) Human PBMCs or CD4+ T cells (105) were stimulated with 105 allogenic irradiated PBMCs with 10 μg/mL control IgG, anti–human CD28 Fab fragments, or 5 μg/mL CTLA4 immunoglobulin, and proliferation was measured after 5 days. Mean ± SD of triplicates from 1 of 8 representative experiments is shown. (B) Purified LEW.1A rat T cells (105) from spleen were stimulated with 2 × 104 irradiated LEW.1W rat dendritic cells, incubated with 5 μg/mL control IgG, anti–rat CD28 Fab fragments, or CTLA4 immunoglobulin and processed as in panel A. Data are mean ± SD of 3 experiments. (C) LEW.1A rats received 1 mg modulating anti–rat CD28 JJ319 intraperitoneally at days 0 and 2, and spleens were collected at day 3; 105 purified T cells were then challenged with 2 × 104 irradiated allogenic dendritic cells without further addition of antibody in vitro. (D) Expression of CD28 on spleen cells from rat treated with modulating anti-CD28 mAb. The white histogram indicates the background level of fluorescence with secondary antibody alone; shaded histogram, spleen lymphocytes at day 3 from a rat treated with 1 mg anti-CD28 mAb at days 0 and 2; and black histogram, spleen lymphocytes at day 3 from a rat treated with 1 mg control IgG at days 0 and 2. *indicates significative at P < .05.
