Figure 5.

Increased T cell responses to old host APCs. (a) Nonirradiated young and old B6D2F1 mice were injected with 5 × 10⁷ splenic lymphocytes from B6.Ly5.2 donors for expansion studies. Spleens were harvested on day 4. Donor T cell phenotype (CD4⁺, CD8⁺, and CD45.1⁺) was determined by FACS analysis as described in Methods. (b–d) Young splenic T cells from B6 mice were cultured with irradiated spleen cells from either young B6D2F1 or old B6D2F1 animals. Proliferation and IL-2 and IFN-γ production were measured as described in Methods. (e) BM-derived DCs were irradiated and cultured with 1 × 10⁵ T cells from B6 mice as described in Methods. T cell proliferation was determined by [³H]thymidine incorporation. P < 0.01, allogeneic T cell responses to old DCs (filled squares) versus young DCs (open squares). (f and g) TNF-α and IL-12 p40 secretion from DCs stimulated with 0.1 μg LPS/ml for 4 hours (TNF-α) or 24 hours (IL-12 p40). Each graph represents one of three similar experiments. *P = 0.03, **P < 0.01.