Proliferation and IFN-γ production of BAL fluid (A) and Splenic (B) T cells to host (CBA) antigens in vitro. CBA mice received BMT as in Fig 1 (syngeneic, allo TCD BM alone •, allo TCD BM and T cells •). BAL cells and splenocytes were obtained from transplanted animals 6 weeks after BMT and cultured with irradiated host stimulator cells as described in Materials and Methods. BAL and splenic T-cell populations from recipients of allogeneic BM and T cells responded to host antigens in vitro. TCD reduced, but did not eliminate, proliferation and IFN-γ production of pulmonary T cells to host antigens, whereas similar responses by splenocytes were absent, consistent with the lack of GVHD in these animals. Values for proliferation were normalized for the percent T cells present in each group (CD4⁺ and CD8⁺). IFN-γ levels expressed in U/mL were measured at maximum proliferative response (200 × 10³ responders per well). Data are expressed as mean ± SEM of triplicate wells and represent one of two similar experiments.