Ability of individual T cells to produce cytokines. Spleen cells were harvested 28 days after allogeneic T-cell-depleted bone marrow transplantation or 42 days after congenic stem cell transplantation. Spleen cells were then stimulated by phorbol 12-myristate 13-acetate and ionomycin in the presence of brefeldin A. Cells were stained with surface markers before fixation and permeabilization. After permeabilization, cells were stained with anticytokine antibody. The stained samples were analyzed by flow cytometry. Irrelevant isotype-matched control antibody produced less than 1% fluorescent cells. The values represent mean ± SD of 3 to 7 animals per group. (A) Allogeneic T-cell-depleted bone marrow transplantation. For IL-2, P < .05 except 10 million TCD BM versus 50 million TCD BM (CD4⁺); P = NS except 10 million TCD BM versus normal BALB/c (CD8⁺). For IFN-γ, P = NS except 10 million TCD BM versus other groups in CD4⁺ (P < .05). (B) Congenic KTLS cell transplantation. IL-2 production by CD8⁺ T cells was not studied due to technical failure. P = NS except 1000 KTLS versus others and normal CD45.1 versus others (IL-2); P = NS except KTLS recipients versus normal (IFN-γ among CD4⁺); P = NS except normal CD45.2 versus others (except 400 KTLS) and 400 KTLS versus normal CD45.1 (IFN-γ among CD8⁺). KTLS indicates c-Kit⁺Thy1.1^lowLin^-/lowSca-1⁺ hematopoietic stem cells; CD45.1 mice, C57BL/Ka, CD45.1, Thy1.1 mice; and CD45.2 mice, C57BL/6, CD45.2, Thy1.2 mice.