TGF-β1 inhibited the expression of Ia and CD86 antigens and CIITA mRNA in Lin⁻c-kit⁺ HPC cultures in the presence of GM-CSF + SCF with or without TNF at day 6. (A) Dose-dependent inhibition on the generation of Ia⁺CD86⁺ cells from murine Lin⁻c-kit⁺ HPCs stimulated with GM-CSF + SCF + TNF at day 6. The data represent the mean value ± SD of the percentage and absolute numbers of Ia⁺CD86⁺ cells observed in more than five experiments. *P < .05 significance as compared with the cultures without addition of TGF-β1. (B) Ia⁺CD86⁺ cells in Lin⁻c-kit⁺ HPC cultures stimulated with the indicated various combinations of cytokines. Quads were set up on the isotype-matched control dot plot. (C) The expression of CIITA mRNA in Lin⁻c-kit⁺ HPC cultures stimulated with indicated various combinations of cytokines. The results are representative of more than three experiments.